feat: add local-first private AI digest workflow

Migrate app code into canonical feature slices, add phone-only AI digest scheduling and review, wire local notification/background task support, and cover the flow with tests.

lib/features/reminders/application/reminder_scheduler.dart

@@ -0,0 +1,27 @@
+import 'package:relationship_saver/features/local/local_models.dart';
+
+/// Schedules and reconciles reminder deliveries for current local state.
+abstract class ReminderScheduler {
+  /// Reconciles platform schedules to match current enabled reminders.
+  Future<void> reconcile(List<ReminderRule> reminders);
+
+  /// Clears all platform-scheduled reminder jobs.
+  Future<void> clearAll();
+
+  /// Requests notification permissions where the platform requires them.
+  Future<bool> requestPermissions();
+}
+
+/// Default scheduler used until platform notifications are integrated.
+class NoopReminderScheduler implements ReminderScheduler {
+  const NoopReminderScheduler();
+
+  @override
+  Future<void> clearAll() async {}
+
+  @override
+  Future<void> reconcile(List<ReminderRule> reminders) async {}
+
+  @override
+  Future<bool> requestPermissions() async => true;
+}