Integrate notification cards with BLoC/Riverpod state layer

Use ConsumerWidget (Riverpod) or BlocBuilder (BLoC) — whichever matches the foundation epic's established pattern — to connect cards to state. If using Riverpod, prefer ref.watch(reminderNotificationsProvider) with select() to narrow rebuilds. If using BLoC, use BlocSelector. For Supabase Realtime, the subscription should be established in the provider/BLoC, not in the widget layer — this ensures proper lifecycle management.

The widget should only react to emitted states, never manage subscriptions directly. Use AutoDispose providers (Riverpod) or close() in BLoC's close() override to handle cleanup. For AnimatedList, maintain a local list in the widget's state synced to the provider's list, using AnimatedList.of(context).removeItem() for removal animations. Avoid calling setState after dispose by checking mounted before any async callback.

Write flutter_test widget tests covering: (1) cards render correctly when provider emits loaded state, (2) skeleton shown when provider is in loading state, (3) error widget shown when provider emits error, (4) card list updates when a new reminder is emitted, (5) escalation card is removed when escalation is resolved in state. Use Riverpod ProviderScope overrides or BLoC's MockBloc to inject controlled state sequences. Verify no lingering subscriptions by asserting provider dispose callbacks are called. Integration test (using flutter_test's integration_test package): subscribe a test Supabase Realtime channel, emit a test event, assert the card list updates.