fix: order date groups chronologically in EmailTreeModel

- Groups now sorted by representative date (newest first) instead of alphabetically
- 'Hoy', 'Ayer', 'Esta semana', 'Semana pasada', 'Hace dos semanas', 'Este mes', meses, años — en orden cronológico correcto

src/ui/models/EmailTreeModel.cpp

@@ -251,31 +251,55 @@ void EmailTreeModel::buildGroups()
         return dateA > dateB;
     });
 
-    // Group by date
-    QMap<QString, QVector<int>> groups; // groupName -> mail indices
+    // Group by date - store both groupName and representative date for sorting
+    struct GroupData {
+        QString name;
+        QDateTime representativeDate; // earliest date in group for sorting
+        QVector<int> mailIndices;
+    };
+    QMap<QString, GroupData> groupsMap;
+    
     for (int idx : indices) {
         if (idx < 0 || idx >= m_emails.size()) continue;
         const QDateTime& dt = m_emails[idx].date();
         if (!dt.isValid()) continue;
         
         QString groupName = groupNameForDate(dt);
-        groups[groupName].append(idx);
+        auto& g = groupsMap[groupName];
+        g.name = groupName;
+        g.mailIndices.append(idx);
+        // Keep the earliest (most recent) date as representative for sorting groups chronologically
+        if (!g.representativeDate.isValid() || dt > g.representativeDate) {
+            g.representativeDate = dt;
+        }
     }
 
-    // Create tree items in group order
-    int groupIdx = 0;
-    for (auto it = groups.constBegin(); it != groups.constEnd(); ++it) {
-        const QString& groupName = it.key();
-        const QVector<int>& mailIndices = it.value();
-        if (mailIndices.isEmpty()) continue;
+    // Sort groups by representative date descending (newest group first)
+    QVector<GroupData> sortedGroups;
+    sortedGroups.reserve(groupsMap.size());
+    for (auto it = groupsMap.constBegin(); it != groupsMap.constEnd(); ++it) {
+        if (!it.value().mailIndices.isEmpty()) {
+            sortedGroups.append(it.value());
+        }
+    }
+    std::sort(sortedGroups.begin(), sortedGroups.end(), [](const GroupData& a, const GroupData& b) {
+        // Newest group first (descending by representative date)
+        if (!a.representativeDate.isValid() && !b.representativeDate.isValid()) return false;
+        if (!a.representativeDate.isValid()) return false;
+        if (!b.representativeDate.isValid()) return true;
+        return a.representativeDate > b.representativeDate;
+    });
 
+    // Create tree items in chronological group order
+    int groupIdx = 0;
+    for (const GroupData& g : sortedGroups) {
         TreeItem* groupItem = new TreeItem(TreeItem::Group, m_rootItem);
-        groupItem->groupName = groupName;
+        groupItem->groupName = g.name;
         groupItem->groupIndex = groupIdx++;
         groupItem->row = m_rootItem->children.size();
         m_rootItem->children.append(groupItem);
 
-        for (int mailIdx : mailIndices) {
+        for (int mailIdx : g.mailIndices) {
             if (mailIdx < 0 || mailIdx >= m_emails.size()) continue;
             TreeItem* mailItem = new TreeItem(TreeItem::Mail, groupItem);
             mailItem->mailIndex = mailIdx;