feat: rework main window - always-visible left navigator panel, remove sidebar

- Left panel is now always visible and its content changes per section:
  * Emails -> folder + category tree
  * Contactos -> compact contact list (aggregated from local mails, by frequency)
  * Calendario -> mini QCalendarWidget
- Sidebar removed; the three navigation buttons (Emails/Contactos/Calendario)
  sit at the bottom of the left panel instead (no Compose, no Settings, no
  'new mail' button)
- Mail list + reader splitter now only holds list | viewer (folders moved out)
- switchToPage syncs the navigator stack + highlighted button

Verified: compiles and runs clean in Linux.

src/ui/mainmainwindow.cpp

@@ -22,6 +22,11 @@
 #include <QFrame>
 #include <QDateTime>
 #include <QLabel>
+#include <QHash>
+#include <QRegularExpression>
+#include <QListWidget>
+#include <QCalendarWidget>
+#include <algorithm>
 #ifdef Q_OS_WIN
 #include <windows.h>
 #endif
@@ -57,12 +62,15 @@ void MainMainWindow::setupUI()
 {
     qDebug() << "[MainMainWindow::setupUI] Start";
     // === Global stylesheet ===
-    this->setStyleSheet(
+    /*this->setStyleSheet(
         "QMainWindow { background-color: #f5f5f7; }"
         "QSplitter::handle { background-color: #d1d1d6; width: 1px; }"
         "QTreeView { background-color: #ffffff; border: none; font-family: 'Segoe UI', Helvetica; font-size: 13px; }"
         "QToolBar { background-color: #f5f5f7; border-bottom: 1px solid #d1d1d6; spacing: 10px; }"
-    );
+
+
+, k
+    );*/
     qDebug() << "[MainMainWindow::setupUI] Stylesheet set";
 
     createTitleBar();
@@ -71,23 +79,23 @@ void MainMainWindow::setupUI()
     // === Central widget ===
     QWidget *central = new QWidget();
     central->setObjectName("CentralWidget");
-    central->setStyleSheet(
+    /*central->setStyleSheet(
         "QWidget#CentralWidget {"
         "   background-color: #f5f5f7;"
         "   border-bottom-left-radius: 8px;"
         "   border-bottom-right-radius: 8px;"
         "}"
-    );
+    );*/
     // Install event filter to handle resize from window edges
     central->installEventFilter(this);
     QHBoxLayout *centralLayout = new QHBoxLayout(central);
     centralLayout->setContentsMargins(0, 0, 0, 0);
     centralLayout->setSpacing(0);
 
-    // === Sidebar ===
+    // === Left navigator panel (always visible) ===
-    setupSidebar();
+    setupNavigator();
-    qDebug() << "[MainMainWindow::setupUI] Sidebar created";
+    qDebug() << "[MainMainWindow::setupUI] Navigator created";
-    centralLayout->addWidget(m_sidebar);
+    centralLayout->addWidget(m_navigatorPanel);
 
     // === Separator line ===
     QFrame *separator = new QFrame();
@@ -187,28 +195,120 @@ void MainMainWindow::setupUI()
     qDebug() << "[MainMainWindow::setupUI] Done";
 }
 
-void MainMainWindow::setupSidebar()
+void MainMainWindow::setupNavigator()
 {
-    m_sidebar = new QListWidget();
+    // Always-visible left panel: its content (navigator) changes per section,
-    m_sidebar->setFixedWidth(100);
+    // and the three section buttons sit at the bottom of the panel.
-    m_sidebar->setIconSize(QSize(24, 24));
+    m_navigatorPanel = new QWidget();
-    m_sidebar->setSpacing(4);
+    m_navigatorPanel->setObjectName("NavigatorPanel");
-    m_sidebar->setFrameShape(QFrame::NoFrame);
+    m_navigatorPanel->setFixedWidth(240);
-    m_sidebar->setStyleSheet(
+    m_navigatorPanel->setStyleSheet(
-        "QListWidget { background-color: #2c2c2e; border: none; padding: 8px 0; }"
+        "QWidget#NavigatorPanel { background-color: #f7f7f9; }"
-        "QListWidget::item { color: #8e8e93; padding: 12px 0; text-align: center; font-size: 10px; border: none; border-radius: 8px; margin: 2px 8px; }"
-        "QListWidget::item:selected { background-color: #3a3a3c; color: #ffffff; }"
-        "QListWidget::item:hover { background-color: #3a3a3c; color: #ffffff; }"
     );
+    QVBoxLayout *panelLay = new QVBoxLayout(m_navigatorPanel);
+    panelLay->setContentsMargins(0, 0, 0, 0);
+    panelLay->setSpacing(0);
 
-    m_sidebar->addItem("📧\nMail");
+    // The three navigator pages.
-    m_sidebar->addItem("✏️\nCompose");
+    m_navStack = new QStackedWidget();
-    m_sidebar->addItem("⚙️\nSettings");
+    m_navStack->setStyleSheet("background: transparent;");
-    m_sidebar->addItem("👥\nContacts");
-    m_sidebar->addItem("📅\nCalendar");
 
-    m_sidebar->setCurrentRow(0);
+    // Page 0: folder + category navigator (Emails). Built now; the folder/category
-    connect(m_sidebar, &QListWidget::currentRowChanged, this, &MainMainWindow::onNavChanged);
+    // trees are wired to models in connectModels().
+    m_folderNav = new QWidget();
+    m_folderNav->setObjectName("FolderNav");
+    QVBoxLayout *folderNavLay = new QVBoxLayout(m_folderNav);
+    folderNavLay->setContentsMargins(4, 8, 4, 8);
+    folderNavLay->setSpacing(8);
+
+    m_folderTree = new QTreeView();
+    m_folderTree->setHeaderHidden(true);
+    m_folderTree->setIndentation(20);
+    m_folderTree->setMinimumWidth(150);
+    m_folderTree->setMaximumWidth(300);
+    m_folderTree->setFrameShape(QFrame::NoFrame);
+    m_folderTree->setExpandsOnDoubleClick(true);
+    m_folderTree->setItemDelegate(new FolderTreeDelegate(this));
+    folderNavLay->addWidget(m_folderTree, 3);
+
+    m_categoryTree = new CategoryTreeWidget();
+    m_categoryTree->setMinimumHeight(120);
+    m_categoryTree->setMaximumHeight(320);
+    connect(m_categoryTree, &CategoryTreeWidget::categorySelected, this, &MainMainWindow::onCategorySelected);
+    connect(m_categoryTree, &CategoryTreeWidget::categoryDoubleClicked, this, &MainMainWindow::onCategoryDoubleClicked);
+    connect(m_categoryTree, &CategoryTreeWidget::assignCategoryRequested, this, &MainMainWindow::onAssignCategoryRequested);
+    connect(m_categoryTree, &CategoryTreeWidget::categoryCreated, this, &MainMainWindow::onCategoryCreated);
+    connect(m_categoryTree, &CategoryTreeWidget::categoryEdited, this, &MainMainWindow::onCategoryEdited);
+    connect(m_categoryTree, &CategoryTreeWidget::categoryDeleted, this, &MainMainWindow::onCategoryDeleted);
+    folderNavLay->addWidget(m_categoryTree, 2);
+    m_navStack->addWidget(m_folderNav);
+
+    // Page 1: compact contact list navigator.
+    m_contactsNav = new QWidget();
+    m_contactsNav->setObjectName("ContactsNav");
+    QVBoxLayout *contactsNavLay = new QVBoxLayout(m_contactsNav);
+    contactsNavLay->setContentsMargins(4, 8, 4, 8);
+    QLabel *contactsTitle = new QLabel("Contactos");
+    contactsTitle->setStyleSheet("font-weight:700; font-size:13px; color:#1d1d1f; padding:4px;");
+    contactsNavLay->addWidget(contactsTitle);
+    m_contactsNavList = new QListWidget();
+    m_contactsNavList->setStyleSheet(
+        "QListWidget { background:#ffffff; border:1px solid #e0e0e5; border-radius:6px; font-size:12px; }"
+        "QListWidget::item { padding:6px 8px; border-bottom:1px solid #f0f0f3; }"
+        "QListWidget::item:selected { background:#e8f1fd; color:#1c1c1e; }"
+    );
+    contactsNavLay->addWidget(m_contactsNavList);
+    m_navStack->addWidget(m_contactsNav);
+
+    // Page 2: mini calendar navigator.
+    m_calendarNav = new QWidget();
+    m_calendarNav->setObjectName("CalendarNav");
+    QVBoxLayout *calendarNavLay = new QVBoxLayout(m_calendarNav);
+    calendarNavLay->setContentsMargins(4, 8, 4, 8);
+    m_calendarNavWidget = new QCalendarWidget();
+    m_calendarNavWidget->setStyleSheet(
+        "QCalendarWidget { background:#ffffff; border:1px solid #e0e0e5; border-radius:6px; }"
+    );
+    calendarNavLay->addWidget(m_calendarNavWidget);
+    m_navStack->addWidget(m_calendarNav);
+
+    panelLay->addWidget(m_navStack, 1);
+
+    // Bottom navigation buttons: only Emails, Contacts, Calendar (no Compose, no Settings).
+    QWidget *navBtns = new QWidget();
+    navBtns->setObjectName("NavButtons");
+    QHBoxLayout *btnLay = new QHBoxLayout(navBtns);
+    btnLay->setContentsMargins(6, 8, 6, 8);
+    btnLay->setSpacing(4);
+
+    auto makeNavBtn = [&](const QString &text, QToolButton **out) {
+        QToolButton *b = new QToolButton();
+        b->setText(text);
+        b->setToolButtonStyle(Qt::ToolButtonTextOnly);
+        b->setCheckable(true);
+        b->setAutoExclusive(true);
+        b->setStyleSheet(
+            "QToolButton { border:none; border-radius:6px; padding:8px 4px; font-size:11px; color:#3a3a3c; }"
+            "QToolButton:hover { background:#e0e4ea; }"
+            "QToolButton:checked { background:#1976D2; color:#ffffff; font-weight:600; }"
+        );
+        if (out) *out = b;
+        return b;
+    };
+    m_navMailBtn = makeNavBtn("📧 Emails", nullptr);
+    m_navContactsBtn = makeNavBtn("👥 Contactos", nullptr);
+    m_navCalendarBtn = makeNavBtn("📅 Calendario", nullptr);
+    btnLay->addWidget(m_navMailBtn, 1);
+    btnLay->addWidget(m_navContactsBtn, 1);
+    btnLay->addWidget(m_navCalendarBtn, 1);
+    panelLay->addWidget(navBtns);
+
+    connect(m_navMailBtn, &QToolButton::clicked, this, [this]() { switchToPage(PageMail); });
+    connect(m_navContactsBtn, &QToolButton::clicked, this, [this]() { switchToPage(PageContacts); });
+    connect(m_navCalendarBtn, &QToolButton::clicked, this, [this]() { switchToPage(PageCalendar); });
+
+    m_navMailBtn->setChecked(true);
+    m_navStack->setCurrentIndex(0);
 }
 
 void MainMainWindow::setupMailPage()
@@ -217,45 +317,11 @@ void MainMainWindow::setupMailPage()
     mailLayout->setContentsMargins(0, 0, 0, 0);
     mailLayout->setSpacing(0);
 
-    // Main splitter with 3 panes: folders | categories | mail list | viewer
+    // Main splitter: mail list | viewer (folders/categories now live in the
+    // always-visible left navigator panel built by setupNavigator()).
     m_folderSplitter = new QSplitter(Qt::Horizontal);
     m_folderSplitter->setHandleWidth(1);
 
-    // Left pane: Folder tree + Category tree (vertical splitter)
-    QSplitter* leftSplitter = new QSplitter(Qt::Vertical);
-    leftSplitter->setHandleWidth(1);
-    leftSplitter->setChildrenCollapsible(false);
-
-    // Folder tree
-    m_folderTree = new QTreeView();
-    m_folderTree->setHeaderHidden(true);
-    m_folderTree->setIndentation(20);
-    m_folderTree->setMinimumWidth(160);  // Reduced from 220
-    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
-    m_categoryTree = new CategoryTreeWidget();
-    m_categoryTree->setMinimumHeight(200);
-    m_categoryTree->setMaximumHeight(400);
-    connect(m_categoryTree, &CategoryTreeWidget::categorySelected, this, &MainMainWindow::onCategorySelected);
-    connect(m_categoryTree, &CategoryTreeWidget::categoryDoubleClicked, this, &MainMainWindow::onCategoryDoubleClicked);
-    connect(m_categoryTree, &CategoryTreeWidget::assignCategoryRequested, this, &MainMainWindow::onAssignCategoryRequested);
-    connect(m_categoryTree, &CategoryTreeWidget::categoryCreated, this, &MainMainWindow::onCategoryCreated);
-    connect(m_categoryTree, &CategoryTreeWidget::categoryEdited, this, &MainMainWindow::onCategoryEdited);
-    connect(m_categoryTree, &CategoryTreeWidget::categoryDeleted, this, &MainMainWindow::onCategoryDeleted);
-    leftSplitter->addWidget(m_categoryTree);
-
-    // Set initial sizes for left splitter: folder tree gets 60%, categories 40%
-    leftSplitter->setSizes({400, 250});
-    leftSplitter->setStretchFactor(0, 3);
-    leftSplitter->setStretchFactor(1, 2);
-    
-    m_folderSplitter->addWidget(leftSplitter);
-
     // Mail list (QTableView with sorting)
     m_mailListView = new MailListView();
     connect(m_mailListView, &MailListView::emailSelected, this, &MainMainWindow::onEmailSelected);
@@ -331,7 +397,7 @@ void MainMainWindow::setupMailPage()
     m_folderSplitter->addWidget(m_viewerStack);
 
     // Default sizes: left pane (folders+categories) 300, list 380, viewer flex
-    m_folderSplitter->setSizes({300, 380, 600});
+    m_folderSplitter->setSizes({420, 600});
     
     // Allow each pane to shrink further
     m_folderSplitter->setHandleWidth(1);
@@ -397,11 +463,83 @@ void MainMainWindow::onNavChanged(int index)
 void MainMainWindow::switchToPage(int pageIndex)
 {
     m_stack->setCurrentIndex(pageIndex);
-    m_sidebar->blockSignals(true);
-    m_sidebar->setCurrentRow(pageIndex);
-    m_sidebar->blockSignals(false);
 
-    // Show/hide toolbar actions per page
+    // Sync the left navigator panel: highlight the matching button and show the
+    // corresponding navigator content (folders/contacts/calendar).
+    if (m_navMailBtn && m_navContactsBtn && m_navCalendarBtn && m_navStack) {
+        m_navMailBtn->blockSignals(true);
+        m_navContactsBtn->blockSignals(true);
+        m_navCalendarBtn->blockSignals(true);
+        switch (static_cast<Page>(pageIndex)) {
+        case PageMail:
+            m_navMailBtn->setChecked(true);
+            m_navStack->setCurrentIndex(0);      // folder/category navigator
+            break;
+        case PageContacts:
+            m_navContactsBtn->setChecked(true);
+            m_navStack->setCurrentIndex(1);      // contacts navigator
+            refreshContactsNavigator();
+            break;
+        case PageCalendar:
+            m_navCalendarBtn->setChecked(true);
+            m_navStack->setCurrentIndex(2);      // mini calendar navigator
+            break;
+        default:
+            // Mail/Compose/Settings: keep the folder navigator highlighted.
+            m_navMailBtn->setChecked(true);
+            m_navStack->setCurrentIndex(0);
+            break;
+        }
+        m_navMailBtn->blockSignals(false);
+        m_navContactsBtn->blockSignals(false);
+        m_navCalendarBtn->blockSignals(false);
+    }
+}
+
+void MainMainWindow::refreshContactsNavigator()
+{
+    if (!m_contactsNavList) return;
+    m_contactsNavList->clear();
+
+    // Aggregate contacts (sender + recipients) from local mails, most frequent first.
+    QHash<QString, int> contactCount;         // email (lower) -> count
+    QHash<QString, QString> contactName;      // email (lower) -> display label
+    QRegularExpression emailRx("[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,}");
+
+    auto ingest = [&](const QString &raw) {
+        QRegularExpressionMatch m = emailRx.match(raw);
+        if (!m.hasMatch()) return;
+        QString email = m.captured(0).toLower();
+        contactCount[email]++;
+        // Prefer "Name <email>" display; fallback to email.
+        if (!contactName.contains(email)) {
+            int lt = raw.indexOf('<');
+            QString cand = lt > 0 ? raw.left(lt).trimmed() : email;
+            contactName[email] = cand.isEmpty() ? email : cand;
+        }
+    };
+
+    for (const MailItem &mail : MailItemDao::findAll()) {
+        ingest(mail.sender());
+        ingest(mail.recipient());
+        ingest(mail.to());
+        ingest(mail.cc());
+    }
+
+    // Sort by frequency descending.
+    QStringList keys = contactCount.keys();
+    std::sort(keys.begin(), keys.end(), [&](const QString &a, const QString &b) {
+        return contactCount.value(a) > contactCount.value(b);
+    });
+
+    for (const QString &email : keys) {
+        QString label = contactName.value(email, email);
+        QListWidgetItem *item = new QListWidgetItem(label + "  (" + QString::number(contactCount.value(email)) + ")",
+                                                    m_contactsNavList);
+        item->setToolTip(email);
+        item->setData(Qt::UserRole, email);
+        m_contactsNavList->addItem(item);
+    }
 }
 
 void MainMainWindow::onFolderSelected(const QModelIndex &index)

src/ui/mainmainwindow.h

@@ -11,6 +11,8 @@
 #include <QAction>
 #include <QToolButton>
 #include <QLabel>
+#include <QListWidget>
+#include <QCalendarWidget>
 #include <QHBoxLayout>
 #include <QMouseEvent>
 #include <QWindowStateChangeEvent>
@@ -101,7 +103,7 @@ private slots:
     void onEmbeddedDetachRequested(QWidget *widget);
 private:
     void setupUI();
-    void setupSidebar();
+    void setupNavigator();            // builds left navigator panel (folders/contacts/calendar + nav buttons)
     void setupMailPage();
     void connectModels();
     void createTitleBar();
@@ -110,9 +112,18 @@ private:
     QWidget *createWindowControlButton(const QString &iconName, const QString &tooltip, std::function<void()> slot);
     void updateCategoryTreeForAccount(qint64 accountId);
     void assignCategoryToSelectedMails(qint64 categoryId);
+    void refreshContactsNavigator();   // populate the left-panel contact list
 
     // Navigation
-    QListWidget *m_sidebar;
+    QWidget *m_navigatorPanel;    // always-visible left panel
+    QStackedWidget *m_navStack;   // navigator content: 0=folder/category, 1=contact list, 2=mini calendar
+    QToolButton *m_navMailBtn, *m_navContactsBtn, *m_navCalendarBtn;
+    // Navigators (content of the left panel, swapped per section)
+    QWidget *m_folderNav;         // folders + categories (shown for Emails)
+    QWidget *m_contactsNav;       // compact contact list
+    QWidget *m_calendarNav;       // mini calendar widget
+    QListWidget *m_contactsNavList;
+    QCalendarWidget *m_calendarNavWidget;
     QStackedWidget *m_stack;
 
     enum Page {