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_notification_intent_bus.dart

@@ -0,0 +1,18 @@
+import 'dart:async';
+
+/// Broadcasts reminder notification tap intents to the UI layer.
+class ReminderNotificationIntentBus {
+  final StreamController<String> _controller =
+      StreamController<String>.broadcast();
+
+  Stream<String> get intents => _controller.stream;
+
+  void emitTap(String reminderId) {
+    if (reminderId.trim().isEmpty) {
+      return;
+    }
+    _controller.add(reminderId.trim());
+  }
+
+  Future<void> close() => _controller.close();
+}