fix(mobile): use JSON maps for nested config compatibility defaults

mobile/lib/utils/openapi_patching.dart

@@ -34,7 +34,9 @@ final Map<String, Map<String, Object?>> openApiPatches = {
       lightStyle: 'https://tiles.immich.cloud/v1/style/light.json',
       darkStyle: 'https://tiles.immich.cloud/v1/style/dark.json',
     ).toJson(),
-    'ffmpeg': PublicConfigFFmpegDto(realtime: PublicConfigFFmpegRealtimeDto(enabled: false)).toJson(),
+    'ffmpeg': {
+      'realtime': {'enabled': false},
+    },
   },
   'ServerConfigDto': {
     'mapLightStyleUrl': 'https://tiles.immich.cloud/v1/style/light.json',
@@ -53,7 +55,11 @@ final Map<String, Map<String, Object?>> openApiPatches = {
   'PeopleResponse': {'updateStrategy': 'everyone'},
   'PersonResponseDto': {'otherPeople': const [], 'sharedBy': const [], 'sharedWith': const []},
   'ServerVersionResponseDto': {'featureLevel': 0},
-  'UserConfigDto': {'notifications': UserConfigNotificationsDto(smtp: UserConfigSmtpDto(enabled: false)).toJson()},
+  'UserConfigDto': {
+    'notifications': {
+      'smtp': {'enabled': false},
+    },
+  },
   'WorkflowResponseDto': {'logging': false},
 };