fix: EmailListModel as QAbstractTableModel for proper MailListView display

- Changed EmailListModel from QAbstractListModel to QAbstractTableModel
- Added columnCount() returning 3 columns (Subject, Sender, Date)
- Added headerData() for column headers (Asunto, De, Fecha)
- Modified data() to handle Qt::DisplayRole per column index
- Updated MailListView::setModel() to use column indices instead of role-based column hiding
- Added proper column resize modes (Stretch for Subject/Sender, ResizeToContents for Date)
- Default sort by Date column descending

src/ui/models/EmailListModel.cpp

@@ -3,7 +3,7 @@
 #include <QDateTime>
 
 EmailListModel::EmailListModel(QObject *parent)
-    : QAbstractListModel(parent)
+    : QAbstractTableModel(parent)
 {
     refresh();
 }
@@ -15,6 +15,12 @@ int EmailListModel::rowCount(const QModelIndex &parent) const
     return m_emails.size();
 }
 
+int EmailListModel::columnCount(const QModelIndex &parent) const
+{
+    Q_UNUSED(parent);
+    return ColCount;
+}
+
 QVariant EmailListModel::data(const QModelIndex &index, int role) const
 {
     if (!index.isValid() || index.row() >= m_emails.size())
@@ -23,6 +29,17 @@ QVariant EmailListModel::data(const QModelIndex &index, int role) const
     const MailItem& item = m_emails.at(index.row());
 
     switch (role) {
+    case Qt::DisplayRole:
+    case Qt::EditRole:
+        switch (index.column()) {
+        case ColSubject:
+            return item.subject();
+        case ColSender:
+            return item.sender();
+        case ColDate:
+            return item.date();
+        }
+        break;
     case IdRole:
         return item.id();
     case SubjectRole:
@@ -49,13 +66,29 @@ QVariant EmailListModel::data(const QModelIndex &index, int role) const
         QString sender = item.sender();
         if (sender.isEmpty())
             return QString();
-        // Get first character, or first non-space character?
-        // Simple: first character of the sender string
         return QString(sender.at(0)).toUpper();
     }
     default:
         return QVariant();
     }
+    return QVariant();
+}
+
+QVariant EmailListModel::headerData(int section, Qt::Orientation orientation, int role) const
+{
+    if (orientation != Qt::Horizontal || role != Qt::DisplayRole)
+        return QVariant();
+
+    switch (section) {
+    case ColSubject:
+        return tr("Asunto");
+    case ColSender:
+        return tr("De");
+    case ColDate:
+        return tr("Fecha");
+    default:
+        return QVariant();
+    }
 }
 
 QHash<int, QByteArray> EmailListModel::roleNames() const