Fix release notification resource and add multiple advance reminders

mobile/lib/app/app_controller.dart

@@ -92,7 +92,10 @@ class AppController extends ChangeNotifier {
   ) => _run(() async {
     final previous = snapshot.settings;
     final value = change(previous);
-    if (![5, 10, 15, 30, 60].contains(value.reminderMinutes)) {
+    if (value.reminderOffsets.isEmpty ||
+        value.reminderOffsets.any(
+          (v) => !AppSettings.allowedReminderMinutes.contains(v),
+        )) {
       throw ArgumentError('提醒时间无效');
     }
     if (!value.courseHeightScale.isFinite ||
@@ -111,7 +114,7 @@ class AppController extends ChangeNotifier {
     final scheduleChanged =
         previous.semester != value.semester ||
         previous.remindersEnabled != value.remindersEnabled ||
-        previous.reminderMinutes != value.reminderMinutes ||
+        !listEquals(previous.reminderOffsets, value.reminderOffsets) ||
         previous.calendarEnabled != value.calendarEnabled ||
         previous.calendarId != value.calendarId;
     if (scheduleChanged) await _reconcile();