feat(04-01): NotificationSettingsNotifier with SharedPreferences persistence and full test suite

- Fix NotificationService API calls to use flutter_local_notifications v21 named parameters
- Expose nextInstanceOf as @visibleForTesting public method for unit testing
- Create NotificationSettingsNotifier with @Riverpod(keepAlive: true)
- NotificationSettings data class with enabled bool + TimeOfDay fields
- Persist notifications_enabled, notifications_hour, notifications_minute to SharedPreferences
- Sync default state in build(), async _load() overrides on hydration
- Update tests to use correct Riverpod 3 provider name (notificationSettingsProvider)
- Add makeContainer() helper to await initial _load() before asserting mutations
- All 84 tests pass (72 existing + 12 new notification tests)

lib/core/notifications/notification_service.dart

@@ -14,15 +14,14 @@ class NotificationService {
     const android = AndroidInitializationSettings('@mipmap/ic_launcher');
     const settings = InitializationSettings(android: android);
     await _plugin.initialize(
-      settings,
+      settings: settings,
       onDidReceiveNotificationResponse: _onTap,
     );
   }
 
   Future<bool> requestPermission() async {
-    final android = _plugin
-        .resolvePlatformSpecificImplementation<
-            AndroidFlutterLocalNotificationsPlugin>();
+    final android = _plugin.resolvePlatformSpecificImplementation<
+        AndroidFlutterLocalNotificationsPlugin>();
     return await android?.requestNotificationsPermission() ?? false;
   }
 
@@ -32,7 +31,7 @@ class NotificationService {
     required String body,
   }) async {
     await _plugin.cancelAll();
-    final scheduledDate = _nextInstanceOf(time);
+    final scheduledDate = nextInstanceOf(time);
     const details = NotificationDetails(
       android: AndroidNotificationDetails(
         'daily_summary',
@@ -43,11 +42,11 @@ class NotificationService {
       ),
     );
     await _plugin.zonedSchedule(
-      0,
+      id: 0,
       title: title,
       body: body,
       scheduledDate: scheduledDate,
-      details,
+      notificationDetails: details,
       androidScheduleMode: AndroidScheduleMode.inexactAllowWhileIdle,
       matchDateTimeComponents: DateTimeComponents.time,
     );

lib/core/notifications/notification_settings_notifier.dart

@@ -0,0 +1,52 @@
+import 'package:flutter/material.dart' show TimeOfDay;
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+part 'notification_settings_notifier.g.dart';
+
+class NotificationSettings {
+  final bool enabled;
+  final TimeOfDay time;
+
+  const NotificationSettings({required this.enabled, required this.time});
+}
+
+@Riverpod(keepAlive: true)
+class NotificationSettingsNotifier extends _$NotificationSettingsNotifier {
+  static const _enabledKey = 'notifications_enabled';
+  static const _hourKey = 'notifications_hour';
+  static const _minuteKey = 'notifications_minute';
+
+  @override
+  NotificationSettings build() {
+    _load();
+    return const NotificationSettings(
+      enabled: false,
+      time: TimeOfDay(hour: 7, minute: 0),
+    );
+  }
+
+  Future<void> _load() async {
+    final prefs = await SharedPreferences.getInstance();
+    final enabled = prefs.getBool(_enabledKey) ?? false;
+    final hour = prefs.getInt(_hourKey) ?? 7;
+    final minute = prefs.getInt(_minuteKey) ?? 0;
+    state = NotificationSettings(
+      enabled: enabled,
+      time: TimeOfDay(hour: hour, minute: minute),
+    );
+  }
+
+  Future<void> setEnabled(bool enabled) async {
+    state = NotificationSettings(enabled: enabled, time: state.time);
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(_enabledKey, enabled);
+  }
+
+  Future<void> setTime(TimeOfDay time) async {
+    state = NotificationSettings(enabled: state.enabled, time: time);
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setInt(_hourKey, time.hour);
+    await prefs.setInt(_minuteKey, time.minute);
+  }
+}

lib/core/notifications/notification_settings_notifier.g.dart

@@ -0,0 +1,65 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'notification_settings_notifier.dart';
+
+// **************************************************************************
+// RiverpodGenerator
+// **************************************************************************
+
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// ignore_for_file: type=lint, type=warning
+
+@ProviderFor(NotificationSettingsNotifier)
+final notificationSettingsProvider = NotificationSettingsNotifierProvider._();
+
+final class NotificationSettingsNotifierProvider
+    extends
+        $NotifierProvider<NotificationSettingsNotifier, NotificationSettings> {
+  NotificationSettingsNotifierProvider._()
+    : super(
+        from: null,
+        argument: null,
+        retry: null,
+        name: r'notificationSettingsProvider',
+        isAutoDispose: false,
+        dependencies: null,
+        $allTransitiveDependencies: null,
+      );
+
+  @override
+  String debugGetCreateSourceHash() => _$notificationSettingsNotifierHash();
+
+  @$internal
+  @override
+  NotificationSettingsNotifier create() => NotificationSettingsNotifier();
+
+  /// {@macro riverpod.override_with_value}
+  Override overrideWithValue(NotificationSettings value) {
+    return $ProviderOverride(
+      origin: this,
+      providerOverride: $SyncValueProvider<NotificationSettings>(value),
+    );
+  }
+}
+
+String _$notificationSettingsNotifierHash() =>
+    r'0d04ca73c4724bb84ce8d92608cd238cb362254a';
+
+abstract class _$NotificationSettingsNotifier
+    extends $Notifier<NotificationSettings> {
+  NotificationSettings build();
+  @$mustCallSuper
+  @override
+  void runBuild() {
+    final ref = this.ref as $Ref<NotificationSettings, NotificationSettings>;
+    final element =
+        ref.element
+            as $ClassProviderElement<
+              AnyNotifier<NotificationSettings, NotificationSettings>,
+              NotificationSettings,
+              Object?,
+              Object?
+            >;
+    element.handleCreate(ref, build);
+  }
+}