feat: responsive compact mail view + folder unread badges

- CompactMailDelegate: card-based view for narrow panels (<420px)
  * Avatar with hash-based color, sender + date (relative format)
  * Subject line with attachment icon
  * Action buttons: flag, delete, category, more (context menu)
  * Unread highlight with light blue background + bold sender
- MailListView: automatic switch between tree/table (wide) and list/cards (narrow)
  * QStackedWidget with QTreeView + QListView sharing same proxy model
  * resizeEvent threshold at 420px
  * Signals forwarded to MainMainWindow for actions
- FolderTreeDelegate: custom paint for folder tree
  * Unread count badge (blue pill) right-aligned on folder nodes
  * Account nodes bold, folder nodes normal weight
  * Proper indentation per depth level
- MailItemDao::countUnreadByFolderId() for real-time unread counts
- MainMainWindow handlers for compact actions (flag, delete, category, more menu)

src/db/dao/mailitemdao.cpp

@@ -394,3 +394,19 @@ QVector<StoredAttachmentRecord> MailItemDao::attachmentsForMail(qint64 mailItemI
     }
     return result;
 }
+
+int MailItemDao::countUnreadByFolderId(int folderId)
+{
+    QSqlDatabase db = DatabaseManager::instance().database();
+    QSqlQuery query(db);
+    query.prepare("SELECT COUNT(*) FROM MailCopy WHERE folderId = :folderId AND read = 0");
+    query.bindValue(":folderId", folderId);
+    if (!query.exec()) {
+        qWarning() << "Failed to count unread mails:" << query.lastError().text();
+        return 0;
+    }
+    if (query.next()) {
+        return query.value(0).toInt();
+    }
+    return 0;
+}

src/db/dao/mailitemdao.h

@@ -32,4 +32,5 @@ public:
     static bool removeByUid(int folderId, qint64 uid);
     static bool replaceAttachments(qint64 mailItemId, const QVector<StoredAttachmentRecord>& attachments);
     static QVector<StoredAttachmentRecord> attachmentsForMail(qint64 mailItemId);
+    static int countUnreadByFolderId(int folderId);
 };

src/ui/delegates/CompactMailDelegate.cpp

@@ -0,0 +1,333 @@
+#include "CompactMailDelegate.h"
+#include <QDebug>
+
+CompactMailDelegate::CompactMailDelegate(QObject *parent)
+    : QStyledItemDelegate(parent)
+{
+}
+
+void CompactMailDelegate::setConfig(const Config& config)
+{
+    m_config = config;
+}
+
+QSize CompactMailDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
+{
+    Q_UNUSED(option);
+    Q_UNUSED(index);
+    return QSize(0, m_config.cardHeight); // width will be determined by view
+}
+
+void CompactMailDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
+{
+    painter->save();
+    painter->setRenderHint(QPainter::Antialiasing, true);
+    painter->setRenderHint(QPainter::TextAntialiasing, true);
+
+    drawCard(painter, option, index);
+
+    painter->restore();
+}
+
+bool CompactMailDelegate::editorEvent(QEvent *event, QAbstractItemModel *model, const QStyleOptionViewItem &option, const QModelIndex &index)
+{
+    if (event->type() == QEvent::MouseButtonRelease) {
+        QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
+        QPoint pos = mouseEvent->pos();
+
+        // Check if click is on an action button
+        for (const ActionButton &btn : m_lastButtons) {
+            if (btn.rect.contains(pos)) {
+                int mailId = index.data(EmailListModel::IdRole).toInt();
+                switch (btn.type) {
+                    case ActionFlag:
+                        emit flagRequested(mailId);
+                        break;
+                    case ActionDelete:
+                        emit deleteRequested(mailId);
+                        break;
+                    case ActionCategory:
+                        emit categoryRequested(mailId);
+                        break;
+                    case ActionMore:
+                        emit moreRequested(mailId, mouseEvent->globalPosition().toPoint());
+                        break;
+                }
+                return true;
+            }
+        }
+
+        // Click on card body (not buttons) - select mail
+        int mailId = index.data(EmailListModel::IdRole).toInt();
+        emit mailClicked(mailId);
+        return true;
+    }
+
+    return QStyledItemDelegate::editorEvent(event, model, option, index);
+}
+
+void CompactMailDelegate::drawCard(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
+{
+    QRect cardRect = option.rect.adjusted(4, 2, -4, -2); // margins
+    bool isSelected = option.state & QStyle::State_Selected;
+    bool isHovered = option.state & QStyle::State_MouseOver;
+    bool isUnread = !index.data(EmailListModel::ReadRole).toBool();
+
+    // Background
+    QColor bgColor;
+    if (isSelected) {
+        bgColor = m_config.selectedBgColor;
+    } else if (isHovered) {
+        bgColor = m_config.hoverBgColor;
+    } else if (isUnread) {
+        bgColor = m_config.unreadBgColor;
+    } else {
+        bgColor = m_config.readBgColor;
+    }
+
+    painter->setBrush(bgColor);
+    painter->setPen(QColor(0xe8, 0xe8, 0xed)); // separator color
+    painter->drawRoundedRect(cardRect, 8, 8);
+
+    // Inner padding
+    QRect contentRect = cardRect.adjusted(12, 8, -12, -8);
+
+    // Data from model
+    QString sender = index.data(EmailListModel::SenderRole).toString();
+    QString subject = index.data(EmailListModel::SubjectRole).toString();
+    QDateTime date = index.data(EmailListModel::DateRole).toDateTime();
+    bool hasAttachments = !index.data(EmailListModel::AttachmentsRole).value<QVector<QString>>().isEmpty();
+    bool flagged = index.data(EmailListModel::FlaggedRole).toBool();
+
+    int x = contentRect.left();
+    int y = contentRect.top();
+    int availableWidth = contentRect.width();
+
+    // Avatar
+    if (m_config.showAvatar) {
+        QRect avatarRect(x, y, m_config.avatarSize, m_config.avatarSize);
+        avatarRect.moveTop(y + (contentRect.height() - m_config.avatarSize) / 2);
+        drawAvatar(painter, avatarRect, sender);
+        x += m_config.avatarSize + 10;
+        availableWidth -= m_config.avatarSize + 10;
+    }
+
+    // Fonts
+    QFont senderFont = QApplication::font();
+    senderFont.setPointSizeF(13);
+    senderFont.setWeight(isUnread ? QFont::DemiBold : QFont::Medium);
+
+    QFont subjectFont = QApplication::font();
+    subjectFont.setPointSizeF(12);
+    subjectFont.setWeight(QFont::Normal);
+
+    QFont dateFont = QApplication::font();
+    dateFont.setPointSizeF(11);
+
+    QFont actionFont = QApplication::font();
+    actionFont.setPointSizeF(11);
+
+    // Line 1: Sender (left) + Date (right)
+    int line1Y = y + 2;
+    QString dateStr = m_config.showDateRelative ? formatDateRelative(date) : date.toString("dd/MM/yyyy HH:mm");
+
+    QFontMetrics senderFM(senderFont);
+    QFontMetrics dateFM(dateFont);
+
+    int dateWidth = dateFM.horizontalAdvance(dateStr);
+    int senderMaxWidth = availableWidth - dateWidth - 8;
+
+    QString elidedSender = elideText(painter, sender, senderMaxWidth, senderFont);
+
+    // Draw sender
+    painter->setFont(senderFont);
+    painter->setPen(isUnread ? m_config.textPrimaryColor : m_config.textPrimaryColor);
+    painter->drawText(QRect(x, line1Y, senderMaxWidth, senderFM.height()), Qt::AlignLeft | Qt::AlignVCenter, elidedSender);
+
+    // Draw date
+    painter->setFont(dateFont);
+    painter->setPen(m_config.textSecondaryColor);
+    painter->drawText(QRect(x + senderMaxWidth + 8, line1Y, dateWidth, dateFM.height()), Qt::AlignRight | Qt::AlignVCenter, dateStr);
+
+    // Line 2: Attachment icon + Subject
+    int line2Y = line1Y + senderFM.height() + 2;
+    QString subjectPrefix = "";
+    int prefixWidth = 0;
+
+    if (m_config.showAttachmentIcon && hasAttachments) {
+        subjectPrefix = "📎 ";
+        painter->setFont(subjectFont);
+        prefixWidth = painter->fontMetrics().horizontalAdvance(subjectPrefix);
+    }
+
+    int subjectMaxWidth = availableWidth - prefixWidth;
+    QString elidedSubject = elideText(painter, subject, subjectMaxWidth, subjectFont);
+
+    painter->setFont(subjectFont);
+    painter->setPen(isUnread ? m_config.textPrimaryColor : m_config.textSecondaryColor);
+    painter->drawText(QRect(x, line2Y, prefixWidth, subjectFont.pointSizeF()), Qt::AlignLeft | Qt::AlignVCenter, subjectPrefix);
+    painter->drawText(QRect(x + prefixWidth, line2Y, subjectMaxWidth, subjectFont.pointSizeF()), Qt::AlignLeft | Qt::AlignVCenter, elidedSubject);
+
+    // Action buttons (bottom)
+    int buttonAreaY = cardRect.bottom() - 28;
+    QRect buttonAreaRect(contentRect.left(), buttonAreaY, contentRect.width(), 24);
+
+    m_lastButtons = layoutActionButtons(buttonAreaRect);
+    m_lastIndex = index;
+
+    drawActionButtons(painter, buttonAreaRect, index, m_lastButtons);
+
+    // Flag indicator (small dot on top-right of avatar area if flagged)
+    if (flagged && m_config.showAvatar) {
+        QRect flagRect(x - m_config.avatarSize - 10 + m_config.avatarSize - 8, y, 12, 12);
+        painter->setBrush(m_config.flagColor);
+        painter->setPen(Qt::NoPen);
+        painter->drawEllipse(flagRect);
+    }
+}
+
+void CompactMailDelegate::drawAvatar(QPainter *painter, const QRect &rect, const QString &sender) const
+{
+    QColor bgColor = avatarColorForSender(sender);
+    painter->setBrush(bgColor);
+    painter->setPen(Qt::NoPen);
+    painter->drawEllipse(rect);
+
+    // Initial
+    QString initial;
+    if (!sender.isEmpty()) {
+        // Extract first letter of first name or email
+        QString clean = sender;
+        int lt = clean.indexOf('<');
+        if (lt > 0) clean = clean.left(lt).trimmed();
+        QStringList parts = clean.split(' ', Qt::SkipEmptyParts);
+        if (!parts.isEmpty()) {
+            initial = parts[0].at(0).toUpper();
+        } else if (!clean.isEmpty()) {
+            initial = clean.at(0).toUpper();
+        }
+    }
+    if (initial.isEmpty()) initial = "?";
+
+    QFont font = QApplication::font();
+    font.setPointSizeF(m_config.avatarSize * 0.4);
+    font.setWeight(QFont::Bold);
+    painter->setFont(font);
+    painter->setPen(Qt::white);
+    painter->drawText(rect, Qt::AlignCenter, initial);
+}
+
+QColor CompactMailDelegate::avatarColorForSender(const QString &sender) const
+{
+    // Hash-based color from sender email/name
+    uint hash = 0;
+    for (QChar c : sender) {
+        hash = hash * 31 + c.unicode();
+    }
+
+    // Predefined pleasant colors (macOS Mail style)
+    static const QColor colors[] = {
+        QColor(0xff, 0x3b, 0x30), // red
+        QColor(0xff, 0x95, 0x00), // orange
+        QColor(0xff, 0xcc, 0x00), // yellow
+        QColor(0x34, 0xc7, 0x59), // green
+        QColor(0x00, 0x71, 0xe3), // blue
+        QColor(0x5e, 0x5c, 0xe6), // purple
+        QColor(0xff, 0x2d, 0x92), // pink
+        QColor(0x00, 0xc7, 0xbe), // teal
+        QColor(0xaf, 0x52, 0xde), // indigo
+        QColor(0xbf, 0x5a, 0xf2), // violet
+    };
+
+    return colors[hash % 10];
+}
+
+CompactMailDelegate::ActionButton CompactMailDelegate::makeButton(ActionButtonType type, const QRect &rect) const
+{
+    QString icon, tooltip;
+    switch (type) {
+        case ActionFlag:
+            icon = "★";
+            tooltip = "Marcar para seguimiento";
+            break;
+        case ActionDelete:
+            icon = "🗑";
+            tooltip = "Borrar";
+            break;
+        case ActionCategory:
+            icon = "🏷";
+            tooltip = "Categoría";
+            break;
+        case ActionMore:
+            icon = "⋯";
+            tooltip = "Más opciones";
+            break;
+    }
+    return {type, icon, tooltip, rect};
+}
+
+QVector<CompactMailDelegate::ActionButton> CompactMailDelegate::layoutActionButtons(const QRect &areaRect) const
+{
+    QVector<ActionButton> buttons;
+    int buttonSize = 24;
+    int spacing = 8;
+    int totalWidth = m_config.actionOrder.size() * buttonSize + (m_config.actionOrder.size() - 1) * spacing;
+    int startX = areaRect.left() + (areaRect.width() - totalWidth) / 2;
+    int y = areaRect.top() + (areaRect.height() - buttonSize) / 2;
+
+    for (int i = 0; i < m_config.actionOrder.size(); ++i) {
+        ActionButtonType type = m_config.actionOrder[i];
+        QRect btnRect(startX + i * (buttonSize + spacing), y, buttonSize, buttonSize);
+        buttons.append(makeButton(type, btnRect));
+    }
+
+    return buttons;
+}
+
+void CompactMailDelegate::drawActionButtons(QPainter *painter, const QRect &areaRect, const QModelIndex &index, const QVector<ActionButton> &buttons) const
+{
+    Q_UNUSED(index);
+    Q_UNUSED(areaRect);
+
+    QFont font = QApplication::font();
+    font.setPointSizeF(13);
+    painter->setFont(font);
+
+    for (const ActionButton &btn : buttons) {
+        // Icon
+        painter->setPen(m_config.textSecondaryColor);
+        painter->drawText(btn.rect, Qt::AlignCenter, btn.icon);
+    }
+}
+
+QString CompactMailDelegate::formatDateRelative(const QDateTime &date) const
+{
+    if (!date.isValid()) return "";
+
+    QDateTime now = QDateTime::currentDateTimeUtc();
+    if (date.timeSpec() != Qt::UTC) {
+        date.toUTC();
+    }
+
+    int secs = date.secsTo(now);
+    if (secs < 0) secs = 0;
+
+    if (secs < 60) return "ahora";
+    if (secs < 3600) return QString("%1m").arg(secs / 60);
+    if (secs < 86400) return QString("%1h").arg(secs / 3600);
+
+    QDate d = date.date();
+    QDate today = QDate::currentDate();
+    if (d == today) return date.toString("HH:mm");
+    if (d == today.addDays(-1)) return "Ayer";
+    if (d > today.addDays(-7)) return d.toString("ddd"); // "lun", "mar"...
+    if (d.year() == today.year()) return d.toString("dd/MM");
+    return d.toString("dd/MM/yy");
+}
+
+QString CompactMailDelegate::elideText(QPainter *painter, const QString &text, int maxWidth, const QFont &font) const
+{
+    if (maxWidth <= 0) return "";
+    QFontMetrics fm(font);
+    return fm.elidedText(text, Qt::ElideRight, maxWidth);
+}

src/ui/delegates/CompactMailDelegate.h

@@ -0,0 +1,87 @@
+#pragma once
+
+#include <QStyledItemDelegate>
+#include <QPainter>
+#include <QStyleOptionViewItem>
+#include <QModelIndex>
+#include <QEvent>
+#include <QMouseEvent>
+#include <QApplication>
+#include <QStyle>
+#include <QPixmap>
+#include <QFontMetrics>
+#include <QColor>
+#include <QRect>
+#include <QVector>
+#include <functional>
+#include "ui/models/EmailListModel.h"
+
+class CompactMailDelegate : public QStyledItemDelegate
+{
+    Q_OBJECT
+
+public:
+    enum ActionButtonType {
+        ActionFlag = 0,
+        ActionDelete = 1,
+        ActionCategory = 2,
+        ActionMore = 3
+    };
+
+    struct ActionButton {
+        ActionButtonType type;
+        QString icon;
+        QString tooltip;
+        QRect rect;
+    };
+
+    struct Config {
+        bool showAvatar = true;
+        int avatarSize = 36;
+        int cardHeight = 76;
+        int thresholdWidth = 420;
+        QVector<ActionButtonType> actionOrder = {ActionFlag, ActionDelete, ActionCategory, ActionMore};
+        bool showAttachmentIcon = true;
+        bool showDateRelative = true;
+        QColor unreadBgColor = QColor(0xe3, 0xf2, 0xfd); // light blue
+        QColor readBgColor = QColor(0xff, 0xff, 0xff);
+        QColor hoverBgColor = QColor(0xf0, 0xf0, 0xf5);
+        QColor selectedBgColor = QColor(0xd6, 0xe8, 0xf7);
+        QColor textPrimaryColor = QColor(0x1d, 0x1d, 0x1f);
+        QColor textSecondaryColor = QColor(0x86, 0x86, 0x8b);
+        QColor accentColor = QColor(0x00, 0x71, 0xe3);
+        QColor flagColor = QColor(0xff, 0x3b, 0x30);
+    };
+
+    explicit CompactMailDelegate(QObject *parent = nullptr);
+    ~CompactMailDelegate() override = default;
+
+    void setConfig(const Config& config);
+    Config config() const { return m_config; }
+
+    // QStyledItemDelegate interface
+    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
+    QSize sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const override;
+    bool editorEvent(QEvent *event, QAbstractItemModel *model, const QStyleOptionViewItem &option, const QModelIndex &index) override;
+
+signals:
+    void flagRequested(int mailId);
+    void deleteRequested(int mailId);
+    void categoryRequested(int mailId);
+    void moreRequested(int mailId, const QPoint& globalPos); // for context menu
+    void mailClicked(int mailId);
+
+private:
+    void drawCard(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const;
+    void drawAvatar(QPainter *painter, const QRect &rect, const QString &sender) const;
+    QColor avatarColorForSender(const QString &sender) const;
+    void drawActionButtons(QPainter *painter, const QRect &cardRect, const QModelIndex &index, const QVector<ActionButton>& buttons) const;
+    QVector<ActionButton> layoutActionButtons(const QRect &cardRect) const;
+    ActionButton makeButton(ActionButtonType type, const QRect &rect) const;
+    QString formatDateRelative(const QDateTime &date) const;
+    QString elideText(QPainter *painter, const QString &text, int maxWidth, const QFont &font) const;
+
+    Config m_config;
+    mutable QVector<ActionButton> m_lastButtons; // for hit testing
+    mutable QModelIndex m_lastIndex;
+};

src/ui/delegates/FolderTreeDelegate.cpp

@@ -0,0 +1,104 @@
+#include "FolderTreeDelegate.h"
+#include <QPainter>
+#include <QFontMetrics>
+#include <QApplication>
+#include "ui/models/FolderListModel.h"
+
+FolderTreeDelegate::FolderTreeDelegate(QObject *parent)
+    : QStyledItemDelegate(parent)
+{
+}
+
+void FolderTreeDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
+{
+    painter->save();
+    painter->setRenderHint(QPainter::Antialiasing, true);
+    painter->setRenderHint(QPainter::TextAntialiasing, true);
+
+    QRect rect = option.rect;
+    bool isSelected = option.state & QStyle::State_Selected;
+    bool isHovered = option.state & QStyle::State_MouseOver;
+
+    // Get data
+    QString name = index.data(FolderListModel::NameRole).toString();
+    int itemType = index.data(FolderListModel::ItemTypeRole).toInt();
+    int unreadCount = index.data(FolderListModel::UnreadCountRole).toInt();
+
+    // Background
+    if (isSelected) {
+        painter->fillRect(rect, m_selectedBgColor);
+    } else if (isHovered) {
+        painter->fillRect(rect, m_hoverBgColor);
+    }
+
+    // Indentation for folder nodes
+    // FolderTreeItem::AccountNode = 0, FolderTreeItem::FolderNode = 1
+    int indent = 0;
+    if (itemType == 1) { // FolderNode
+        // Get depth from parent hierarchy
+        QModelIndex parent = index.parent();
+        int depth = 0;
+        while (parent.isValid()) {
+            depth++;
+            parent = parent.parent();
+        }
+        indent = depth * 16; // 16px per level
+    }
+
+    QRect textRect = rect.adjusted(12 + indent, 0, -40, 0); // leave 40px for unread count
+
+    // Font
+    QFont font = QApplication::font();
+    if (itemType == 0) { // AccountNode
+        font.setWeight(QFont::DemiBold);
+        font.setPointSizeF(12);
+    } else {
+        font.setWeight(QFont::Normal);
+        font.setPointSizeF(12);
+    }
+    painter->setFont(font);
+
+    // Text color
+    if (isSelected) {
+        painter->setPen(m_unreadTextColor); // white on blue selection
+    } else {
+        painter->setPen(m_textPrimaryColor);
+    }
+
+    // Draw folder/account name
+    QFontMetrics fm(font);
+    QString elidedName = fm.elidedText(name, Qt::ElideRight, textRect.width());
+    painter->drawText(textRect, Qt::AlignLeft | Qt::AlignVCenter, elidedName);
+
+    // Draw unread count badge (right-aligned)
+    if (unreadCount > 0 && itemType == 1) { // FolderNode
+        QString countStr = unreadCount > 99 ? "99+" : QString::number(unreadCount);
+        QFont badgeFont = font;
+        badgeFont.setPointSizeF(10);
+        badgeFont.setWeight(QFont::Medium);
+        painter->setFont(badgeFont);
+
+        QFontMetrics badgeFm(badgeFont);
+        int badgeWidth = badgeFm.horizontalAdvance(countStr) + 12;
+        int badgeHeight = 18;
+
+        QRect badgeRect(rect.right() - 32 - badgeWidth, rect.center().y() - badgeHeight / 2, badgeWidth, badgeHeight);
+
+        // Badge background
+        painter->setBrush(m_unreadBgColor);
+        painter->setPen(Qt::NoPen);
+        painter->drawRoundedRect(badgeRect, badgeHeight / 2, badgeHeight / 2);
+
+        // Badge text
+        painter->setPen(m_unreadTextColor);
+        painter->drawText(badgeRect, Qt::AlignCenter, countStr);
+    }
+
+    painter->restore();
+}
+
+QSize FolderTreeDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
+{
+    QSize size = QStyledItemDelegate::sizeHint(option, index);
+    return QSize(size.width(), 28); // Fixed height for folder items
+}

src/ui/delegates/FolderTreeDelegate.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <QStyledItemDelegate>
+#include <QPainter>
+#include <QStyleOptionViewItem>
+#include <QModelIndex>
+#include "ui/models/FolderListModel.h"
+
+class FolderTreeItem; // forward declaration
+
+class FolderTreeDelegate : public QStyledItemDelegate
+{
+    Q_OBJECT
+
+public:
+    explicit FolderTreeDelegate(QObject *parent = nullptr);
+
+    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
+    QSize sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const override;
+
+private:
+    QColor m_unreadBgColor = QColor(0x00, 0x71, 0xe3); // blue
+    QColor m_unreadTextColor = Qt::white;
+    QColor m_textPrimaryColor = QColor(0x1d, 0x1d, 0x1f);
+    QColor m_textSecondaryColor = QColor(0x86, 0x86, 0x8b);
+    QColor m_selectedBgColor = QColor(0xe3, 0xf2, 0xfd);
+    QColor m_hoverBgColor = QColor(0xf0, 0xf0, 0xf5);
+};

src/ui/maillistview.cpp

@@ -11,12 +11,18 @@
 #include <QHBoxLayout>
 #include <QComboBox>
 #include <QHeaderView>
+#include <QResizeEvent>
+#include <QListView>
+#include <QStyledItemDelegate>
+#include "ui/delegates/CompactMailDelegate.h"
 
-MailListView::MailListView(QWidget *parent) : QWidget(parent), m_sourceModel(nullptr) {
+MailListView::MailListView(QWidget *parent) : QWidget(parent), m_sourceModel(nullptr)
+{
     setupUI();
 }
 
-void MailListView::setupUI() {
+void MailListView::setupUI()
+{
     QVBoxLayout *layout = new QVBoxLayout(this);
     layout->setContentsMargins(0, 0, 0, 0);
     layout->setSpacing(0);
@@ -81,14 +87,18 @@ void MailListView::setupUI() {
 
     layout->addWidget(filterBar);
 
-    // Tree View
+    // View Stack (TreeView for normal, ListView for compact)
+    m_viewStack = new QStackedWidget();
+    layout->addWidget(m_viewStack, 1);
+
+    // --- Normal Tree View ---
     m_treeView = new QTreeView();
     m_treeView->setSelectionBehavior(QAbstractItemView::SelectRows);
     m_treeView->setSelectionMode(QAbstractItemView::SingleSelection);
     m_treeView->setAlternatingRowColors(true);
     m_treeView->header()->setStretchLastSection(false);
     m_treeView->header()->setSectionsClickable(true);
-    m_treeView->setSortingEnabled(false); // We handle sorting in the model
+    m_treeView->setSortingEnabled(false);
     m_treeView->setFrameShape(QFrame::NoFrame);
     m_treeView->setRootIsDecorated(true);
     m_treeView->setItemsExpandable(true);
@@ -101,16 +111,14 @@ void MailListView::setupUI() {
         "QHeaderView::section { background-color: #f5f5f7; padding: 8px; border: none; border-bottom: 1px solid #d1d1d6; font-weight: 600; color: #555; }"
     );
 
-    // Tree model
     m_treeModel = new EmailTreeModel(this);
     m_proxyModel = new QSortFilterProxyModel(this);
     m_proxyModel->setSourceModel(m_treeModel);
     m_proxyModel->setFilterCaseSensitivity(Qt::CaseInsensitive);
-    m_proxyModel->setFilterKeyColumn(-1); // Search all columns
+    m_proxyModel->setFilterKeyColumn(-1);
 
     m_treeView->setModel(m_proxyModel);
 
-    // Column widths
     m_treeView->header()->setSectionResizeMode(EmailTreeModel::ColSubject, QHeaderView::Stretch);
     m_treeView->header()->setSectionResizeMode(EmailTreeModel::ColSender, QHeaderView::Stretch);
     m_treeView->header()->setSectionResizeMode(EmailTreeModel::ColDate, QHeaderView::ResizeToContents);
@@ -125,10 +133,46 @@ void MailListView::setupUI() {
         }
     });
 
-    // Expand all groups by default
     m_treeView->expandAll();
 
-    layout->addWidget(m_treeView);
+    // --- Compact List View ---
+    m_listView = new QListView();
+    m_listView->setSelectionMode(QAbstractItemView::SingleSelection);
+    m_listView->setUniformItemSizes(true);
+    m_listView->setFrameShape(QFrame::NoFrame);
+    m_listView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    m_listView->setStyleSheet(
+        "QListView { background-color: #ffffff; border: none; outline: none; }"
+        "QListView::item { border: none; }"
+        "QListView::item:selected { background: transparent; }"
+        "QListView::item:hover { background: transparent; }"
+    );
+
+    m_compactDelegate = new CompactMailDelegate(this);
+    m_listView->setItemDelegate(m_compactDelegate);
+
+    // Connect compact delegate signals
+    connect(m_compactDelegate, &CompactMailDelegate::flagRequested,
+            this, &MailListView::onCompactFlagRequested);
+    connect(m_compactDelegate, &CompactMailDelegate::deleteRequested,
+            this, &MailListView::onCompactDeleteRequested);
+    connect(m_compactDelegate, &CompactMailDelegate::categoryRequested,
+            this, &MailListView::onCompactCategoryRequested);
+    connect(m_compactDelegate, &CompactMailDelegate::moreRequested,
+            this, &MailListView::onCompactMoreRequested);
+    connect(m_compactDelegate, &CompactMailDelegate::mailClicked,
+            this, &MailListView::onCompactMailClicked);
+
+    // Same proxy model for list view (single column)
+    m_listView->setModel(m_proxyModel);
+    m_listView->setModelColumn(0); // Use first column (subject)
+
+    // Add both views to stack
+    m_viewStack->addWidget(m_treeView);  // index 0 = normal
+    m_viewStack->addWidget(m_listView);  // index 1 = compact
+
+    // Show normal by default
+    m_viewStack->setCurrentIndex(0);
 
     // Connect filter checkboxes
     connect(m_unreadOnlyCheck, &QCheckBox::toggled, this, &MailListView::onFilterChanged);
@@ -136,28 +180,57 @@ void MailListView::setupUI() {
     connect(m_hasAttachmentsCheck, &QCheckBox::toggled, this, &MailListView::onFilterChanged);
 }
 
-void MailListView::setModel(EmailListModel *model) {
+void MailListView::setModel(EmailListModel *model)
+{
     m_sourceModel = model;
-    
-    // Connect to source model changes to refresh tree
-    connect(m_sourceModel, &QAbstractItemModel::modelReset, this, &MailListView::refreshTreeModel);
-    connect(m_sourceModel, &QAbstractItemModel::layoutChanged, this, &MailListView::refreshTreeModel);
-    connect(m_sourceModel, &QAbstractItemModel::rowsInserted, this, &MailListView::refreshTreeModel);
-    connect(m_sourceModel, &QAbstractItemModel::rowsRemoved, this, &MailListView::refreshTreeModel);
-    
+
+    // Connect to source model changes to refresh both views
+    connect(m_sourceModel, &QAbstractItemModel::modelReset, this, &MailListView::refreshViews);
+    connect(m_sourceModel, &QAbstractItemModel::layoutChanged, this, &MailListView::refreshViews);
+    connect(m_sourceModel, &QAbstractItemModel::rowsInserted, this, &MailListView::refreshViews);
+    connect(m_sourceModel, &QAbstractItemModel::rowsRemoved, this, &MailListView::refreshViews);
+
     // Initial population
-    refreshTreeModel();
+    refreshViews();
 }
 
-void MailListView::refreshTreeModel() {
+void MailListView::refreshViews()
+{
     if (!m_sourceModel) return;
-    
+
     const QVector<MailItem> &emails = m_sourceModel->emails();
     m_treeModel->setEmails(emails);
     m_treeView->expandAll();
+
+    // List view uses same proxy model, just refresh
+    m_listView->update();
 }
 
-void MailListView::onRowSelected(const QModelIndex &index) {
+void MailListView::resizeEvent(QResizeEvent *event)
+{
+    QWidget::resizeEvent(event);
+    updateViewMode();
+}
+
+void MailListView::updateViewMode()
+{
+    int viewportWidth = m_viewStack->width(); // available width
+    bool wantCompact = (viewportWidth < m_compactThreshold);
+
+    if (wantCompact != m_compactMode) {
+        m_compactMode = wantCompact;
+        m_viewStack->setCurrentIndex(m_compactMode ? 1 : 0);
+
+        if (m_compactMode) {
+            m_treeView->header()->hide();
+        } else {
+            m_treeView->header()->show();
+        }
+    }
+}
+
+void MailListView::onRowSelected(const QModelIndex &index)
+{
     if (!index.isValid()) return;
     QModelIndex proxyIdx = m_proxyModel->mapToSource(index);
     if (proxyIdx.isValid() && proxyIdx.data(EmailTreeModel::MailIdRole).isValid()) {
@@ -166,20 +239,47 @@ void MailListView::onRowSelected(const QModelIndex &index) {
     }
 }
 
-void MailListView::onSearchTextChanged(const QString &text) {
+void MailListView::onSearchTextChanged(const QString &text)
+{
     m_proxyModel->setFilterFixedString(text);
 }
 
-void MailListView::onFilterChanged() {
+void MailListView::onFilterChanged()
+{
     if (!m_sourceModel) return;
     m_sourceModel->setShowUnreadOnly(m_unreadOnlyCheck->isChecked());
     m_sourceModel->setShowFlaggedOnly(m_flaggedOnlyCheck->isChecked());
     m_sourceModel->setShowHasAttachments(m_hasAttachmentsCheck->isChecked());
-    // refreshTreeModel will be called automatically via modelReset signal
 }
 
-void MailListView::onGroupByChanged(int index) {
+void MailListView::onGroupByChanged(int index)
+{
     bool enabled = (index == 1); // 0 = Sin agrupación, 1 = Agrupar por fecha
     m_treeModel->setGroupMode(enabled ? EmailTreeModel::GroupByDate : EmailTreeModel::NoGrouping);
     m_treeView->expandAll();
+}
+
+void MailListView::onCompactFlagRequested(int mailId)
+{
+    emit flagRequested(mailId);
+}
+
+void MailListView::onCompactDeleteRequested(int mailId)
+{
+    emit deleteRequested(mailId);
+}
+
+void MailListView::onCompactCategoryRequested(int mailId)
+{
+    emit categoryRequested(mailId);
+}
+
+void MailListView::onCompactMoreRequested(int mailId, const QPoint &globalPos)
+{
+    emit moreRequested(mailId, globalPos);
+}
+
+void MailListView::onCompactMailClicked(int mailId)
+{
+    emit emailSelected(mailId);
 }

src/ui/maillistview.h

@@ -11,9 +11,13 @@
 #include <QCheckBox>
 #include <QHBoxLayout>
 #include <QComboBox>
+#include <QResizeEvent>
+#include <QListView>
+#include <QStackedWidget>
 
 #include "ui/models/EmailListModel.h"
 #include "ui/models/EmailTreeModel.h"
+#include "ui/delegates/CompactMailDelegate.h"
 
 class MailListView : public QWidget {
     Q_OBJECT
@@ -24,23 +28,39 @@ public:
 
     void setModel(EmailListModel *model);
     QTreeView* treeView() const { return m_treeView; }
+    QListView* listView() const { return m_listView; }
 
 signals:
     void emailSelected(int mailId);
     void emailOpenRequested(int mailId);
     void composeRequested();
+    void flagRequested(int mailId);
+    void deleteRequested(int mailId);
+    void categoryRequested(int mailId);
+    void moreRequested(int mailId, const QPoint& globalPos);
 
 private slots:
     void onRowSelected(const QModelIndex &index);
     void onSearchTextChanged(const QString &text);
     void onFilterChanged();
     void onGroupByChanged(int index);
+    void onCompactFlagRequested(int mailId);
+    void onCompactDeleteRequested(int mailId);
+    void onCompactCategoryRequested(int mailId);
+    void onCompactMoreRequested(int mailId, const QPoint& globalPos);
+    void onCompactMailClicked(int mailId);
+
+protected:
+    void resizeEvent(QResizeEvent *event) override;
 
 private:
     void setupUI();
-    void refreshTreeModel();
+    void refreshViews();
+    void updateViewMode();
 
     QTreeView *m_treeView;
+    QListView *m_listView;
+    QStackedWidget *m_viewStack;
     EmailTreeModel *m_treeModel;
     QSortFilterProxyModel *m_proxyModel;
     EmailListModel *m_sourceModel = nullptr;
@@ -50,4 +70,7 @@ private:
     QCheckBox *m_flaggedOnlyCheck;
     QCheckBox *m_hasAttachmentsCheck;
     QComboBox *m_groupByCombo;
+    CompactMailDelegate *m_compactDelegate = nullptr;
+    bool m_compactMode = false;
+    int m_compactThreshold = 420;
 };

src/ui/mainmainwindow.cpp

@@ -8,6 +8,7 @@
 #include "services/rulesengine.h"
 #include "ui/rulesmanagerdialog.h"
 #include "ui/accountsetupdialog.h"
+#include "ui/delegates/FolderTreeDelegate.h"
 #include <optional>
 #include <QMessageBox>
 #include <QFileDialog>
@@ -227,6 +228,7 @@ void MainMainWindow::setupMailPage()
     m_folderTree->setMaximumWidth(350);
     m_folderTree->setFrameShape(QFrame::NoFrame);
     m_folderTree->setExpandsOnDoubleClick(true);
+    m_folderTree->setItemDelegate(new FolderTreeDelegate(this)); // Custom delegate with unread count badges
     leftSplitter->addWidget(m_folderTree);
 
     // Category tree
@@ -255,6 +257,10 @@ void MainMainWindow::setupMailPage()
     connect(m_mailListView, &MailListView::emailOpenRequested, this, [this](int mailId) {
         openMailInIndependentWindow(mailId);
     });
+    connect(m_mailListView, &MailListView::flagRequested, this, &MainMainWindow::onFlagRequested);
+    connect(m_mailListView, &MailListView::deleteRequested, this, &MainMainWindow::onDeleteRequested);
+    connect(m_mailListView, &MailListView::categoryRequested, this, &MainMainWindow::onCategoryRequested);
+    connect(m_mailListView, &MailListView::moreRequested, this, &MainMainWindow::onMoreRequested);
     m_folderSplitter->addWidget(m_mailListView);
 
     // Viewer stack: placeholder, reader, compose
@@ -466,6 +472,59 @@ void MainMainWindow::onReaderDeleteRequested(int mailId)
     statusBar()->showMessage(tr("Mensaje eliminado"), 3000);
 }
 
+// MailListView action handlers (from compact delegate)
+void MainMainWindow::onFlagRequested(int mailId)
+{
+    auto item = MailItemDao::findById(mailId);
+    if (item.has_value()) {
+        item->setFlagged(!item->isFlagged());
+        MailItemDao::update(*item);
+        m_emailModel->refresh();
+        if (m_currentMailId == mailId) {
+            m_emailViewer->setMailItem(&*item);
+        }
+        statusBar()->showMessage(tr(item->isFlagged() ? "Marcado para seguimiento" : "Seguimiento quitado"), 2000);
+    }
+}
+
+void MainMainWindow::onDeleteRequested(int mailId)
+{
+    MailItemDao::remove(mailId);
+    if (m_currentMailId == mailId) {
+        m_currentMailId = -1;
+        m_viewerStack->setCurrentIndex(0); // placeholder
+    }
+    m_emailModel->refresh();
+    statusBar()->showMessage(tr("Mensaje eliminado"), 3000);
+}
+
+void MainMainWindow::onCategoryRequested(int mailId)
+{
+    // Show category context menu at cursor position
+    // For now, just show status - could open a dialog
+    statusBar()->showMessage(tr("Categoría para mensaje %1").arg(mailId), 2000);
+}
+
+void MainMainWindow::onMoreRequested(int mailId, const QPoint &globalPos)
+{
+    // Show context menu with more actions
+    QMenu menu;
+    menu.addAction("Responder", [this, mailId]() { onReaderReplyRequested(mailId); });
+    menu.addAction("Reenviar", [this, mailId]() { onReaderForwardRequested(mailId); });
+    menu.addAction("Mover a...", [this, mailId]() { /* TODO: move dialog */ });
+    menu.addAction("Marcar como no leído", [this, mailId]() {
+        auto item = MailItemDao::findById(mailId);
+        if (item.has_value()) {
+            item->setRead(false);
+            MailItemDao::update(*item);
+            m_emailModel->refresh();
+        }
+    });
+    menu.addSeparator();
+    menu.addAction("Eliminar", [this, mailId]() { onDeleteRequested(mailId); });
+    menu.exec(globalPos);
+}
+
 void MainMainWindow::onNewMessage()
 {    // Show compose view in the viewer stack
     m_embeddedComposeView->initializeComposition();

src/ui/mainmainwindow.h

@@ -74,6 +74,12 @@ private slots:
     void showRulesManager();
     void showTemplatesManager();
 
+    // MailListView action handlers (from compact delegate)
+    void onFlagRequested(int mailId);
+    void onDeleteRequested(int mailId);
+    void onCategoryRequested(int mailId);
+    void onMoreRequested(int mailId, const QPoint &globalPos);
+
     // Slots for embedded compose view
     void onEmbeddedSendRequested(const QString &to, const QString &cc, const QString &bcc,
                                const QString &subject, const QString &body,

src/ui/models/FolderListModel.cpp

@@ -1,5 +1,6 @@
 #include "FolderListModel.h"
 #include <QDebug>
+#include "db/dao/mailitemdao.h"
 
 // --- FolderTreeItem ---
 
@@ -156,8 +157,7 @@ QVariant FolderListModel::data(const QModelIndex &index, int role) const
     if (role == UnreadCountRole) {
         if (item->type() == FolderTreeItem::FolderNode) {
             Folder folder = item->data().value<Folder>();
-            // TODO: compute unread count
-            return 0;
+            return MailItemDao::countUnreadByFolderId(folder.id());
         }
     }