feat: Multi-selection + action bar in MailListView

- MailListView: ExtendedSelection mode for both tree and list views
- Action bar (blue bar) appears when items selected
- Select all checkbox + counter label
- Batch actions: Flag, Mark unread, Move (TODO), Delete, Exit selection
- Signals: selectionChanged, batchFlagRequested, batchDeleteRequested, batchMarkUnreadRequested, batchMoveRequested
- enterMultiSelectMode()/exitMultiSelectMode() state management
- Works in both normal and compact views

src/ui/maillistview.cpp

@@ -15,9 +15,11 @@
 #include <QListView>
 #include <QStyledItemDelegate>
 #include <QScrollBar>
+#include <QToolButton>
+#include <QMenu>
 #include "ui/delegates/CompactMailDelegate.h"
 
-MailListView::MailListView(QWidget *parent) : QWidget(parent), m_sourceModel(nullptr)
+MailListView::MailListView(QWidget *parent) : QWidget(parent), m_sourceModel(nullptr), m_multiSelectMode(false)
 {
     setupUI();
 }
@@ -110,6 +112,67 @@ void MailListView::setupUI()
 
     layout->addWidget(filterBar);
 
+    // Action bar (hidden by default, shown when multi-select mode active)
+    m_actionBar = new QWidget();
+    m_actionBar->setFixedHeight(44);
+    m_actionBar->setStyleSheet("background-color: #e3f2fd; border-bottom: 1px solid #bbdefb;");
+    m_actionBar->setVisible(false);
+    QHBoxLayout *actionBarLayout = new QHBoxLayout(m_actionBar);
+    actionBarLayout->setContentsMargins(12, 4, 12, 4);
+    actionBarLayout->setSpacing(8);
+
+    m_selectAllCheck = new QCheckBox("Seleccionar todo");
+    m_selectAllCheck->setStyleSheet("QCheckBox { font-size: 13px; color: #1d1d1f; }");
+    connect(m_selectAllCheck, &QCheckBox::toggled, this, &MailListView::onSelectAllToggled);
+    actionBarLayout->addWidget(m_selectAllCheck);
+
+    QLabel *selectionLabel = new QLabel("0 elementos seleccionados");
+    selectionLabel->setStyleSheet("font-size: 13px; color: #1d1d1f; font-weight: 500;");
+    selectionLabel->setObjectName("selectionLabel");
+    actionBarLayout->addWidget(selectionLabel);
+
+    actionBarLayout->addStretch();
+
+    // Action buttons
+    auto createActionButton = [&](const QString& text, std::function<void()> slot) -> QToolButton* {
+        QToolButton *btn = new QToolButton();
+        btn->setText(text);
+        btn->setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
+        btn->setStyleSheet(
+            "QToolButton { background: white; border: 1px solid #d1d1d6; border-radius: 6px; "
+            "padding: 6px 12px; font-size: 12px; color: #1d1d1f; }"
+            "QToolButton:hover { background: #f0f0f5; border-color: #bdbdbd; }"
+            "QToolButton:pressed { background: #e0e0e5; }"
+        );
+        connect(btn, &QToolButton::clicked, this, slot);
+        return btn;
+    };
+
+    QToolButton *btnFlag = createActionButton("★ Marcar", [this]() { onBatchFlagClicked(); });
+    actionBarLayout->addWidget(btnFlag);
+
+    QToolButton *btnUnread = createActionButton("✎ No leído", [this]() { onBatchMarkUnreadClicked(); });
+    actionBarLayout->addWidget(btnUnread);
+
+    QToolButton *btnMove = createActionButton("↗ Mover", [this]() { onBatchMoveClicked(); });
+    actionBarLayout->addWidget(btnMove);
+
+    QToolButton *btnDelete = createActionButton("🗑 Borrar", [this]() { onBatchDeleteClicked(); });
+    btnDelete->setStyleSheet(btnDelete->styleSheet() + "QToolButton { color: #ff3b30; border-color: #ff3b30; }");
+    actionBarLayout->addWidget(btnDelete);
+
+    QToolButton *btnExit = new QToolButton();
+    btnExit->setText("✕ Salir selección");
+    btnExit->setToolButtonStyle(Qt::ToolButtonTextOnly);
+    btnExit->setStyleSheet(
+        "QToolButton { padding: 6px 12px; font-size: 12px; color: #0071e3; }"
+        "QToolButton:hover { background: #e8f0fe; border-radius: 6px; }"
+    );
+    connect(btnExit, &QToolButton::clicked, this, [this]() { exitMultiSelectMode(); });
+    actionBarLayout->addWidget(btnExit);
+
+    layout->insertWidget(1, m_actionBar); // Insert after search bar
+
     // View Stack (TreeView for normal, ListView for compact)
     m_viewStack = new QStackedWidget();
     layout->addWidget(m_viewStack, 1);
@@ -117,7 +180,7 @@ void MailListView::setupUI()
     // --- Normal Tree View ---
     m_treeView = new QTreeView();
     m_treeView->setSelectionBehavior(QAbstractItemView::SelectRows);
-    m_treeView->setSelectionMode(QAbstractItemView::SingleSelection);
+    m_treeView->setSelectionMode(QAbstractItemView::ExtendedSelection); // Multi-selection
     m_treeView->setAlternatingRowColors(true);
     m_treeView->header()->setStretchLastSection(false);
     m_treeView->header()->setSectionsClickable(true);
@@ -146,11 +209,12 @@ void MailListView::setupUI()
     m_treeView->header()->setSectionResizeMode(EmailTreeModel::ColSender, QHeaderView::Stretch);
     m_treeView->header()->setSectionResizeMode(EmailTreeModel::ColDate, QHeaderView::ResizeToContents);
 
-    connect(m_treeView, &QTreeView::clicked, this, &MailListView::onRowSelected);
+    connect(m_treeView->selectionModel(), &QItemSelectionModel::selectionChanged,
+            this, &MailListView::onSelectionChanged);
     connect(m_treeView, &QTreeView::doubleClicked, this, [this](const QModelIndex &index) {
         if (!index.isValid()) return;
         QModelIndex proxyIdx = m_proxyModel->mapToSource(index);
-        
+
         // Check if it's a thread node - toggle expansion
         if (proxyIdx.isValid() && proxyIdx.data(EmailTreeModel::IsThreadRole).toBool()) {
             QString threadId = proxyIdx.data(EmailTreeModel::ThreadIdRole).toString();
@@ -160,7 +224,7 @@ void MailListView::setupUI()
                 return;
             }
         }
-        
+
         // Otherwise open mail
         if (proxyIdx.isValid() && proxyIdx.data(EmailTreeModel::MailIdRole).isValid()) {
             int mailId = proxyIdx.data(EmailTreeModel::MailIdRole).toInt();
@@ -172,7 +236,7 @@ void MailListView::setupUI()
 
     // --- Compact List View ---
     m_listView = new QListView();
-    m_listView->setSelectionMode(QAbstractItemView::SingleSelection);
+    m_listView->setSelectionMode(QAbstractItemView::ExtendedSelection); // Multi-selection
     m_listView->setUniformItemSizes(true);
     m_listView->setFrameShape(QFrame::NoFrame);
     m_listView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
@@ -197,11 +261,20 @@ void MailListView::setupUI()
             this, &MailListView::onCompactMoreRequested);
     connect(m_compactDelegate, &CompactMailDelegate::mailClicked,
             this, &MailListView::onCompactMailClicked);
+    connect(m_compactDelegate, &CompactMailDelegate::replyRequested,
+            this, &MailListView::onCompactReplyRequested);
+    connect(m_compactDelegate, &CompactMailDelegate::forwardRequested,
+            this, &MailListView::onCompactForwardRequested);
+    connect(m_compactDelegate, &CompactMailDelegate::markUnreadRequested,
+            this, &MailListView::onCompactMarkUnreadRequested);
 
     // Same proxy model for list view (single column)
     m_listView->setModel(m_proxyModel);
     m_listView->setModelColumn(0); // Use first column (subject)
 
+    connect(m_listView->selectionModel(), &QItemSelectionModel::selectionChanged,
+            this, &MailListView::onSelectionChanged);
+
     // Add both views to stack
     m_viewStack->addWidget(m_treeView);  // index 0 = normal
     m_viewStack->addWidget(m_listView);  // index 1 = compact
@@ -271,13 +344,82 @@ void MailListView::updateViewMode()
     }
 }
 
-void MailListView::onRowSelected(const QModelIndex &index)
+QVector<int> MailListView::getSelectedMailIds() const
 {
-    if (!index.isValid()) return;
-    QModelIndex proxyIdx = m_proxyModel->mapToSource(index);
-    if (proxyIdx.isValid() && proxyIdx.data(EmailTreeModel::MailIdRole).isValid()) {
-        int mailId = proxyIdx.data(EmailTreeModel::MailIdRole).toInt();
-        emit emailSelected(mailId);
+    QVector<int> mailIds;
+    QAbstractItemView *currentView = qobject_cast<QAbstractItemView*>(m_viewStack->currentWidget());
+    QItemSelectionModel *selectionModel = currentView->selectionModel();
+
+    if (!selectionModel) return mailIds;
+
+    QModelIndexList selectedIndexes = selectionModel->selectedRows();
+    for (const QModelIndex &proxyIdx : selectedIndexes) {
+        QModelIndex sourceIdx = m_proxyModel->mapToSource(proxyIdx);
+        if (sourceIdx.isValid() && sourceIdx.data(EmailTreeModel::MailIdRole).isValid()) {
+            int mailId = sourceIdx.data(EmailTreeModel::MailIdRole).toInt();
+            mailIds.append(mailId);
+        }
+    }
+    return mailIds;
+}
+
+void MailListView::updateActionBar()
+{
+    QLabel *label = m_actionBar->findChild<QLabel*>("selectionLabel");
+    if (label) {
+        label->setText(QString("%1 elementos seleccionados").arg(m_selectedMailIds.size()));
+    }
+
+    m_selectAllCheck->blockSignals(true);
+    m_selectAllCheck->setChecked(m_selectedMailIds.size() > 0);
+    m_selectAllCheck->blockSignals(false);
+}
+
+void MailListView::onSelectionChanged()
+{
+    m_selectedMailIds = getSelectedMailIds();
+    bool hasSelection = !m_selectedMailIds.isEmpty();
+
+    if (hasSelection && !m_multiSelectMode) {
+        enterMultiSelectMode();
+    } else if (!hasSelection && m_multiSelectMode) {
+        exitMultiSelectMode();
+    }
+
+    updateActionBar();
+    emit selectionChanged(m_selectedMailIds);
+}
+
+void MailListView::enterMultiSelectMode()
+{
+    m_multiSelectMode = true;
+    m_actionBar->setVisible(true);
+    updateActionBar();
+}
+
+void MailListView::exitMultiSelectMode()
+{
+    m_multiSelectMode = false;
+    m_selectedMailIds.clear();
+    m_actionBar->setVisible(false);
+
+    // Clear selections
+    m_treeView->clearSelection();
+    m_listView->clearSelection();
+    m_selectAllCheck->blockSignals(true);
+    m_selectAllCheck->setChecked(false);
+    m_selectAllCheck->blockSignals(false);
+    updateActionBar();
+    emit selectionChanged(QVector<int>());
+}
+
+void MailListView::onSelectAllToggled(bool checked)
+{
+    QAbstractItemView *currentView = qobject_cast<QAbstractItemView*>(m_viewStack->currentWidget());
+    if (checked) {
+        currentView->selectAll();
+    } else {
+        currentView->clearSelection();
     }
 }
 
@@ -314,46 +456,6 @@ void MailListView::onGroupByChanged(int index)
     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);
-}
-
-void MailListView::onCompactReplyRequested(int mailId)
-{
-    emit replyRequested(mailId);
-}
-
-void MailListView::onCompactForwardRequested(int mailId)
-{
-    emit forwardRequested(mailId);
-}
-
-void MailListView::onCompactMarkUnreadRequested(int mailId)
-{
-    emit markUnreadRequested(mailId);
-}
-
 void MailListView::onDisplayModeChanged(int index)
 {
     CompactMailDelegate::DisplayMode mode = static_cast<CompactMailDelegate::DisplayMode>(index);
@@ -398,4 +500,85 @@ void MailListView::onRowsInserted(const QModelIndex &parent, int first, int last
         m_treeModel->setEmails(emails);
         m_treeView->expandAll();
     }
+}
+
+void MailListView::onRowSelected(const QModelIndex &index)
+{
+    if (!index.isValid()) return;
+    QModelIndex proxyIdx = m_proxyModel->mapToSource(index);
+    if (proxyIdx.isValid() && proxyIdx.data(EmailTreeModel::MailIdRole).isValid()) {
+        int mailId = proxyIdx.data(EmailTreeModel::MailIdRole).toInt();
+        emit emailSelected(mailId);
+    }
+}
+
+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);
+}
+
+void MailListView::onCompactReplyRequested(int mailId)
+{
+    emit replyRequested(mailId);
+}
+
+void MailListView::onCompactForwardRequested(int mailId)
+{
+    emit forwardRequested(mailId);
+}
+
+void MailListView::onCompactMarkUnreadRequested(int mailId)
+{
+    emit markUnreadRequested(mailId);
+}
+
+// Batch action slots
+void MailListView::onBatchFlagClicked()
+{
+    if (m_selectedMailIds.isEmpty()) return;
+    emit batchFlagRequested(m_selectedMailIds, true);
+    exitMultiSelectMode();
+}
+
+void MailListView::onBatchMarkUnreadClicked()
+{
+    if (m_selectedMailIds.isEmpty()) return;
+    emit batchMarkUnreadRequested(m_selectedMailIds);
+    exitMultiSelectMode();
+}
+
+void MailListView::onBatchMoveClicked()
+{
+    if (m_selectedMailIds.isEmpty()) return;
+    // TODO: Show folder picker dialog
+    // For now, just emit signal
+    // emit batchMoveRequested(m_selectedMailIds, targetFolderId);
+    exitMultiSelectMode();
+}
+
+void MailListView::onBatchDeleteClicked()
+{
+    if (m_selectedMailIds.isEmpty()) return;
+    emit batchDeleteRequested(m_selectedMailIds);
+    exitMultiSelectMode();
 }

src/ui/maillistview.h

@@ -41,6 +41,12 @@ signals:
     void replyRequested(int mailId);
     void forwardRequested(int mailId);
     void markUnreadRequested(int mailId);
+    // Multi-selection signals
+    void selectionChanged(const QVector<int>& selectedMailIds);
+    void batchFlagRequested(const QVector<int>& mailIds, bool flagged);
+    void batchDeleteRequested(const QVector<int>& mailIds);
+    void batchMarkUnreadRequested(const QVector<int>& mailIds);
+    void batchMoveRequested(const QVector<int>& mailIds, int targetFolderId);
 
 private slots:
     void onRowSelected(const QModelIndex &index);
@@ -60,6 +66,14 @@ private slots:
     void onTreeViewScrolled(int value);
     void onListViewScrolled(int value);
     void onRowsInserted(const QModelIndex &parent, int first, int last);
+    void onSelectionChanged();
+    void onSelectAllToggled(bool checked);
+    void onBatchFlagClicked();
+    void onBatchMarkUnreadClicked();
+    void onBatchMoveClicked();
+    void onBatchDeleteClicked();
+    void enterMultiSelectMode();
+    void exitMultiSelectMode();
 
 protected:
     void resizeEvent(QResizeEvent *event) override;
@@ -68,6 +82,8 @@ private:
     void setupUI();
     void refreshViews();
     void updateViewMode();
+    void updateActionBar();
+    QVector<int> getSelectedMailIds() const;
 
     QTreeView *m_treeView;
     QListView *m_listView;
@@ -81,9 +97,13 @@ private:
     QCheckBox *m_flaggedOnlyCheck;
     QCheckBox *m_hasAttachmentsCheck;
     QCheckBox *m_pinnedOnlyCheck;
+    QCheckBox *m_selectAllCheck;  // Select all checkbox in action bar
+    QWidget *m_actionBar;  // Action bar widget
     QComboBox *m_groupByCombo;
     QComboBox *m_displayModeCombo;
     CompactMailDelegate *m_compactDelegate = nullptr;
     bool m_compactMode = false;
     int m_compactThreshold = 650;
+    bool m_multiSelectMode = false;
+    QVector<int> m_selectedMailIds;
 };