- 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)
- Tests for default state (enabled=false, time=07:00)
- Tests for setEnabled persistence to SharedPreferences
- Tests for setTime persistence to SharedPreferences
- Tests for loading persisted values via _load()
- Tests for NotificationService singleton pattern
- Tests for nextInstanceOf timezone logic (future/past time)
