refactor(notifications): migrate to layered architecture
- Add controllers: IndexController, SettingsController, ClearController
- Add use cases: GetNotificationListUseCase, SaveSettingsUseCase, ClearNotificationsUseCase
- Add NotificationRepositoryInterface and EloquentNotificationRepository
- Add AuthorizedUserMiddleware; replace legacy user check in routes
- Replace legacy catch-all route with clean URLs: /notifications/, /notifications/settings/, /notifications/clear/
- Migrate Installer to src/Install/ with updated namespace
- Add config/services.php with DI wiring and Counters class alias
- Update templates: remove layout args, add output escaping
- Fix guestbook_comment → guestbook_comments counter key bug
- Remove legacy index.php and includes/
- Add use cases: GetNotificationListUseCase, SaveSettingsUseCase, ClearNotificationsUseCase
- Add NotificationRepositoryInterface and EloquentNotificationRepository
- Add AuthorizedUserMiddleware; replace legacy user check in routes
- Replace legacy catch-all route with clean URLs: /notifications/, /notifications/settings/, /notifications/clear/
- Migrate Installer to src/Install/ with updated namespace
- Add config/services.php with DI wiring and Counters class alias
- Update templates: remove layout args, add output escaping
- Fix guestbook_comment → guestbook_comments counter key bug
- Remove legacy index.php and includes/