feat(04-01): Android config, NotificationService, DAO queries, timezone init, ARB strings

- Add flutter_local_notifications ^21.0.0, timezone ^0.11.0, flutter_timezone ^1.0.8 to pubspec.yaml
- Set compileSdk=35, enable core library desugaring in build.gradle.kts
- Add POST_NOTIFICATIONS, RECEIVE_BOOT_COMPLETED permissions and boot receivers to AndroidManifest.xml
- Create NotificationService singleton with initialize, requestPermission, scheduleDailyNotification, cancelAll
- Add getOverdueAndTodayTaskCount and getOverdueTaskCount one-shot queries to DailyPlanDao
- Initialize timezone and NotificationService in main.dart before runApp
- Add 7 notification-related ARB strings to app_de.arb
- All 72 existing tests pass

lib/core/notifications/notification_service.dart

@@ -0,0 +1,80 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart' show TimeOfDay;
+import 'package:flutter_local_notifications/flutter_local_notifications.dart';
+import 'package:timezone/timezone.dart' as tz;
+
+class NotificationService {
+  static final NotificationService _instance = NotificationService._internal();
+  factory NotificationService() => _instance;
+  NotificationService._internal();
+
+  final _plugin = FlutterLocalNotificationsPlugin();
+
+  Future<void> initialize() async {
+    const android = AndroidInitializationSettings('@mipmap/ic_launcher');
+    const settings = InitializationSettings(android: android);
+    await _plugin.initialize(
+      settings,
+      onDidReceiveNotificationResponse: _onTap,
+    );
+  }
+
+  Future<bool> requestPermission() async {
+    final android = _plugin
+        .resolvePlatformSpecificImplementation<
+            AndroidFlutterLocalNotificationsPlugin>();
+    return await android?.requestNotificationsPermission() ?? false;
+  }
+
+  Future<void> scheduleDailyNotification({
+    required TimeOfDay time,
+    required String title,
+    required String body,
+  }) async {
+    await _plugin.cancelAll();
+    final scheduledDate = _nextInstanceOf(time);
+    const details = NotificationDetails(
+      android: AndroidNotificationDetails(
+        'daily_summary',
+        'Tägliche Zusammenfassung',
+        channelDescription: 'Tägliche Aufgaben-Erinnerung',
+        importance: Importance.defaultImportance,
+        priority: Priority.defaultPriority,
+      ),
+    );
+    await _plugin.zonedSchedule(
+      0,
+      title: title,
+      body: body,
+      scheduledDate: scheduledDate,
+      details,
+      androidScheduleMode: AndroidScheduleMode.inexactAllowWhileIdle,
+      matchDateTimeComponents: DateTimeComponents.time,
+    );
+  }
+
+  Future<void> cancelAll() => _plugin.cancelAll();
+
+  /// Computes the next occurrence of [time] as a [tz.TZDateTime].
+  /// Returns today if [time] is still in the future, tomorrow otherwise.
+  @visibleForTesting
+  tz.TZDateTime nextInstanceOf(TimeOfDay time) {
+    final now = tz.TZDateTime.now(tz.local);
+    var scheduled = tz.TZDateTime(
+      tz.local,
+      now.year,
+      now.month,
+      now.day,
+      time.hour,
+      time.minute,
+    );
+    if (scheduled.isBefore(now)) {
+      scheduled = scheduled.add(const Duration(days: 1));
+    }
+    return scheduled;
+  }
+
+  static void _onTap(NotificationResponse response) {
+    // Navigation to Home tab — wired in Plan 02 via global navigator key
+  }
+}

lib/features/home/data/daily_plan_dao.dart

@@ -32,6 +32,28 @@ class DailyPlanDao extends DatabaseAccessor<AppDatabase>
     });
   }
 
+  /// One-shot count of overdue + today tasks (for notification body).
+  Future<int> getOverdueAndTodayTaskCount({DateTime? today}) async {
+    final now = today ?? DateTime.now();
+    final endOfToday = DateTime(now.year, now.month, now.day + 1);
+    final result = await (selectOnly(tasks)
+          ..addColumns([tasks.id.count()])
+          ..where(tasks.nextDueDate.isSmallerThanValue(endOfToday)))
+        .getSingle();
+    return result.read(tasks.id.count()) ?? 0;
+  }
+
+  /// One-shot count of overdue tasks only (for notification body split).
+  Future<int> getOverdueTaskCount({DateTime? today}) async {
+    final now = today ?? DateTime.now();
+    final startOfToday = DateTime(now.year, now.month, now.day);
+    final result = await (selectOnly(tasks)
+          ..addColumns([tasks.id.count()])
+          ..where(tasks.nextDueDate.isSmallerThanValue(startOfToday)))
+        .getSingle();
+    return result.read(tasks.id.count()) ?? 0;
+  }
+
   /// Count task completions recorded today.
   /// Uses customSelect with readsFrom for proper stream invalidation.
   Stream<int> watchCompletionsToday({DateTime? today}) {

lib/l10n/app_de.arb

@@ -88,5 +88,23 @@
   "dailyPlanAllClearTitle": "Alles erledigt! \ud83c\udf1f",
   "dailyPlanAllClearMessage": "Keine Aufgaben f\u00fcr heute. Genie\u00dfe den Moment!",
   "dailyPlanNoOverdue": "Keine \u00fcberf\u00e4lligen Aufgaben",
-  "dailyPlanNoTasks": "Noch keine Aufgaben angelegt"
+  "dailyPlanNoTasks": "Noch keine Aufgaben angelegt",
+  "settingsSectionNotifications": "Benachrichtigungen",
+  "notificationsEnabledLabel": "Tägliche Erinnerung",
+  "notificationsTimeLabel": "Uhrzeit",
+  "notificationsPermissionDeniedHint": "Benachrichtigungen sind in den Systemeinstellungen deaktiviert. Tippe hier, um sie zu aktivieren.",
+  "notificationTitle": "Dein Tagesplan",
+  "notificationBody": "{count} Aufgaben fällig",
+  "@notificationBody": {
+    "placeholders": {
+      "count": { "type": "int" }
+    }
+  },
+  "notificationBodyWithOverdue": "{count} Aufgaben fällig ({overdue} überfällig)",
+  "@notificationBodyWithOverdue": {
+    "placeholders": {
+      "count": { "type": "int" },
+      "overdue": { "type": "int" }
+    }
+  }
 }

lib/main.dart

@@ -1,9 +1,17 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_timezone/flutter_timezone.dart';
+import 'package:timezone/data/latest_all.dart' as tz;
+import 'package:timezone/timezone.dart' as tz;
 
 import 'package:household_keeper/app.dart';
+import 'package:household_keeper/core/notifications/notification_service.dart';
 
-void main() {
+void main() async {
   WidgetsFlutterBinding.ensureInitialized();
+  tz.initializeTimeZones();
+  final timeZoneName = await FlutterTimezone.getLocalTimezone();
+  tz.setLocalLocation(tz.getLocation(timeZoneName));
+  await NotificationService().initialize();
   runApp(const ProviderScope(child: App()));
 }