feat: move-to-folder dialog, batch actions, reader source view, Focused/Other pivot

- MoveToFolderDialog: modal folder picker per account (excludes current)
- Wire 'Mover a...' in reader ⋯ menu + batch move (emit -1 -> dialog)
- Connect batch delete/mark-unread/flag handlers (were unconnected)
- Reader: 'Ver codigo fuente' reads .eml via MimeStorageService::readEmlFile
- Reader: 'Marcar como no leido' emits markUnreadRequested
- Pivot Focused/Other: EmailListModel::setShowFocusedOnly heuristic
  (flagged/pinned/frequent senders), reset to Focused on inbox select

src/ui/maillistview.cpp

@@ -660,9 +660,8 @@ void MailListView::onBatchMarkUnreadClicked()
 void MailListView::onBatchMoveClicked()
 {
     if (m_selectedMailIds.isEmpty()) return;
-    // TODO: Show folder picker dialog
-    // For now, just emit signal
-    // emit batchMoveRequested(m_selectedMailIds, targetFolderId);
+    // targetFolderId == -1 signals the UI layer to present a folder picker
+    emit batchMoveRequested(m_selectedMailIds, -1);
     exitMultiSelectMode();
 }
 
@@ -678,19 +677,30 @@ void MailListView::setFolderType(const QString& folderType)
     m_pivotCombo->setVisible(folderType == "inbox");
 }
 
+void MailListView::resetPivot()
+{
+    // Default to Focused (index 0). blockSignals to avoid recursive refresh.
+    m_pivotCombo->blockSignals(true);
+    m_pivotCombo->setCurrentIndex(0);
+    m_pivotCombo->blockSignals(false);
+    if (m_sourceModel) {
+        m_sourceModel->setShowFocusedOnly(true);
+        m_sourceModel->refresh();
+    }
+    refreshViews();
+}
+
 void MailListView::onPivotChanged(int index)
 {
     // 0 = Focused (Principal), 1 = Other (Otros)
-    // TODO: Implement pivot filtering logic
-    // For now, just update the model filter
     if (!m_sourceModel) return;
-    
+
     if (index == 0) {
-        // Focused: important emails (could be based on sender frequency, AI, etc.)
-        // m_sourceModel->setShowFocusedOnly(true);
+        // Focused: important emails (flagged, pinned, or frequent senders)
+        m_sourceModel->setShowFocusedOnly(true);
     } else {
-        // Other: promotional, notifications, etc.
-        // m_sourceModel->setShowFocusedOnly(false);
+        // Other: show everything (promotional, notifications, etc.)
+        m_sourceModel->setShowFocusedOnly(false);
     }
     refreshViews();
 }