Fix async init problem with SettingsService

lib/di_initialization.dart

@@ -30,11 +30,9 @@ Future<void> dependencyInjectionInitialization() async {
   final timelineManager = TimelineManager();
   final galleryService = GalleryService();
 
-  getIt.registerSingletonAsync(() async {
-    final service = SettingsService();
-    await service.initialize();
-    return service;
-  });
+  final service = SettingsService();
+  await service.initialize();
+  getIt.registerSingleton<SettingsService>(service);
 
   final objectBoxCache = await ObjectBoxCache.create();
   getIt.registerSingleton<ObjectBoxCache>(objectBoxCache);