Add feedback service, reminder diagnostics and smooth week transitions

mobile/test/services/notification_service_test.dart

@@ -12,6 +12,7 @@ class AlarmGateway extends ReminderGateway {
   ReminderPermissions permission = const ReminderPermissions(true, true);
   final alarms = <int, ReminderRequest>{};
   int permissionRequests = 0;
+  bool dropWrites = false;
   @override
   Future<ReminderPermissions> permissions({required bool request}) async {
     if (request) permissionRequests++;
@@ -22,7 +23,7 @@ class AlarmGateway extends ReminderGateway {
   Future<Set<int>> pendingIds() async => alarms.keys.toSet();
   @override
   Future<void> schedule(ReminderRequest value) async {
-    alarms[value.id] = value;
+    if (!dropWrites) alarms[value.id] = value;
   }
 
   @override
@@ -47,6 +48,23 @@ void main() {
     return AppSnapshot.fromJson(json).settings;
   }
 
+  test(
+    'does not report success when native scheduling did not persist',
+    () async {
+      gateway.dropWrites = true;
+      final events = ScheduleEngine.occurrences([course()], term);
+      await expectLater(
+        service.reconcile(events, settings, DateTime.utc(2026, 9, 9)),
+        throwsA(
+          isA<ReminderSetupException>().having(
+            (e) => e.code,
+            'code',
+            'schedule_not_saved',
+          ),
+        ),
+      );
+    },
+  );
   test(
     'selected advance times produce independent alarms and survive refresh',
     () async {