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/core/notifications/notification_service.dart

@@ -3,6 +3,8 @@ import 'package:flutter/material.dart' show TimeOfDay;
 import 'package:flutter_local_notifications/flutter_local_notifications.dart';
 import 'package:timezone/timezone.dart' as tz;
 
+import 'package:household_keeper/core/router/router.dart';
+
 class NotificationService {
   static final NotificationService _instance = NotificationService._internal();
   factory NotificationService() => _instance;
@@ -74,6 +76,6 @@ class NotificationService {
   }
 
   static void _onTap(NotificationResponse response) {
-    // Navigation to Home tab — wired in Plan 02 via global navigator key
+    router.go('/');
   }
 }

lib/features/settings/presentation/settings_screen.dart

@@ -1,17 +1,101 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import 'package:household_keeper/core/notifications/notification_service.dart';
+import 'package:household_keeper/core/notifications/notification_settings_notifier.dart';
+import 'package:household_keeper/core/providers/database_provider.dart';
 import 'package:household_keeper/core/theme/theme_provider.dart';
+import 'package:household_keeper/features/home/data/daily_plan_dao.dart';
 import 'package:household_keeper/l10n/app_localizations.dart';
 
-class SettingsScreen extends ConsumerWidget {
+class SettingsScreen extends ConsumerStatefulWidget {
   const SettingsScreen({super.key});
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  ConsumerState<SettingsScreen> createState() => _SettingsScreenState();
+}
+
+class _SettingsScreenState extends ConsumerState<SettingsScreen> {
+  Future<void> _onNotificationToggle(bool value) async {
+    if (value) {
+      // Enabling: request permission first
+      final granted = await NotificationService().requestPermission();
+      if (!granted) {
+        // Permission denied — show SnackBar to guide user to system settings
+        if (!mounted) return;
+        final l10n = AppLocalizations.of(context);
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(
+            content: Text(l10n.notificationsPermissionDeniedHint),
+          ),
+        );
+        // Toggle stays OFF — do not update state
+        return;
+      }
+      // Permission granted: enable and schedule
+      await ref
+          .read(notificationSettingsProvider.notifier)
+          .setEnabled(true);
+      await _scheduleNotification();
+    } else {
+      // Disabling: update state and cancel
+      await ref
+          .read(notificationSettingsProvider.notifier)
+          .setEnabled(false);
+      await NotificationService().cancelAll();
+    }
+  }
+
+  Future<void> _scheduleNotification() async {
+    final settings = ref.read(notificationSettingsProvider);
+    if (!settings.enabled) return;
+
+    final db = ref.read(appDatabaseProvider);
+    final dao = DailyPlanDao(db);
+    final total = await dao.getOverdueAndTodayTaskCount();
+    final overdue = await dao.getOverdueTaskCount();
+
+    if (total == 0) {
+      // No tasks today — skip notification
+      await NotificationService().cancelAll();
+      return;
+    }
+
+    if (!mounted) return;
+    final l10n = AppLocalizations.of(context);
+    final body = overdue > 0
+        ? l10n.notificationBodyWithOverdue(total, overdue)
+        : l10n.notificationBody(total);
+    final title = l10n.notificationTitle;
+
+    await NotificationService().scheduleDailyNotification(
+      time: settings.time,
+      title: title,
+      body: body,
+    );
+  }
+
+  Future<void> _onPickTime() async {
+    final settings = ref.read(notificationSettingsProvider);
+    final picked = await showTimePicker(
+      context: context,
+      initialTime: settings.time,
+      initialEntryMode: TimePickerEntryMode.dial,
+    );
+    if (picked != null) {
+      await ref
+          .read(notificationSettingsProvider.notifier)
+          .setTime(picked);
+      await _scheduleNotification();
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
     final l10n = AppLocalizations.of(context);
     final theme = Theme.of(context);
     final currentThemeMode = ref.watch(themeProvider);
+    final notificationSettings = ref.watch(notificationSettingsProvider);
 
     return ListView(
       children: [
@@ -59,7 +143,36 @@ class SettingsScreen extends ConsumerWidget {
 
         const Divider(indent: 16, endIndent: 16, height: 32),
 
-        // Section 2: About (Ueber)
+        // Section 2: Notifications (Benachrichtigungen)
+        Padding(
+          padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
+          child: Text(
+            l10n.settingsSectionNotifications,
+            style: theme.textTheme.titleMedium?.copyWith(
+              color: theme.colorScheme.primary,
+            ),
+          ),
+        ),
+        SwitchListTile(
+          title: Text(l10n.notificationsEnabledLabel),
+          value: notificationSettings.enabled,
+          onChanged: _onNotificationToggle,
+        ),
+        // Progressive disclosure: time picker only when enabled
+        AnimatedSize(
+          duration: const Duration(milliseconds: 200),
+          child: notificationSettings.enabled
+              ? ListTile(
+                  title: Text(l10n.notificationsTimeLabel),
+                  trailing: Text(notificationSettings.time.format(context)),
+                  onTap: _onPickTime,
+                )
+              : const SizedBox.shrink(),
+        ),
+
+        const Divider(indent: 16, endIndent: 16, height: 32),
+
+        // Section 3: About (Ueber)
         Padding(
           padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
           child: Text(

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

lib/l10n/app_localizations_de.dart

@@ -210,4 +210,30 @@ class AppLocalizationsDe extends AppLocalizations {
 
   @override
   String get dailyPlanNoTasks => 'Noch keine Aufgaben angelegt';
+
+  @override
+  String get settingsSectionNotifications => 'Benachrichtigungen';
+
+  @override
+  String get notificationsEnabledLabel => 'Tägliche Erinnerung';
+
+  @override
+  String get notificationsTimeLabel => 'Uhrzeit';
+
+  @override
+  String get notificationsPermissionDeniedHint =>
+      'Benachrichtigungen sind in den Systemeinstellungen deaktiviert. Tippe hier, um sie zu aktivieren.';
+
+  @override
+  String get notificationTitle => 'Dein Tagesplan';
+
+  @override
+  String notificationBody(int count) {
+    return '$count Aufgaben fällig';
+  }
+
+  @override
+  String notificationBodyWithOverdue(int count, int overdue) {
+    return '$count Aufgaben fällig ($overdue überfällig)';
+  }
 }