feat(04-02): wire notification settings UI, permission flow, scheduling, and tap navigation

- Convert SettingsScreen from ConsumerWidget to ConsumerStatefulWidget
- Add Benachrichtigungen section between Darstellung and Uber sections
- SwitchListTile with permission request on toggle ON (Android 13+)
- Toggle reverts to OFF on permission denial with SnackBar hint
- AnimatedSize progressive disclosure for time picker row when enabled
- _scheduleNotification() queries DailyPlanDao for task/overdue counts
- Skip notification scheduling when task count is 0
- Notification body includes overdue split when overdue > 0
- _onPickTime() shows Material 3 showTimePicker dialog then reschedules
- Wire router.go('/') in NotificationService._onTap for tap navigation
- Regenerate AppLocalizations with 7 new notification strings from Plan 01 ARB

lib/l10n/app_localizations.dart

@@ -471,6 +471,48 @@ abstract class AppLocalizations {
   /// In de, this message translates to:
   /// **'Noch keine Aufgaben angelegt'**
   String get dailyPlanNoTasks;
+
+  /// No description provided for @settingsSectionNotifications.
+  ///
+  /// In de, this message translates to:
+  /// **'Benachrichtigungen'**
+  String get settingsSectionNotifications;
+
+  /// No description provided for @notificationsEnabledLabel.
+  ///
+  /// In de, this message translates to:
+  /// **'Tägliche Erinnerung'**
+  String get notificationsEnabledLabel;
+
+  /// No description provided for @notificationsTimeLabel.
+  ///
+  /// In de, this message translates to:
+  /// **'Uhrzeit'**
+  String get notificationsTimeLabel;
+
+  /// No description provided for @notificationsPermissionDeniedHint.
+  ///
+  /// In de, this message translates to:
+  /// **'Benachrichtigungen sind in den Systemeinstellungen deaktiviert. Tippe hier, um sie zu aktivieren.'**
+  String get notificationsPermissionDeniedHint;
+
+  /// No description provided for @notificationTitle.
+  ///
+  /// In de, this message translates to:
+  /// **'Dein Tagesplan'**
+  String get notificationTitle;
+
+  /// No description provided for @notificationBody.
+  ///
+  /// In de, this message translates to:
+  /// **'{count} Aufgaben fällig'**
+  String notificationBody(int count);
+
+  /// No description provided for @notificationBodyWithOverdue.
+  ///
+  /// In de, this message translates to:
+  /// **'{count} Aufgaben fällig ({overdue} überfällig)'**
+  String notificationBodyWithOverdue(int count, int overdue);
 }
 
 class _AppLocalizationsDelegate