👽 Support new attachment reference system

lib/models/user.dart

@@ -31,12 +31,10 @@ sealed class SnAccountProfile with _$SnAccountProfile {
     required String? middleName,
     required String? lastName,
     @Default('') String bio,
-    required String? pictureId,
     required int experience,
     required int level,
     required double levelingProgress,
     required SnCloudFile? picture,
-    required String? backgroundId,
     required SnCloudFile? background,
     required DateTime createdAt,
     required DateTime updatedAt,