👽 Adopt the new folder system (w.i.p)

lib/models/folder.dart

@@ -0,0 +1,19 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'folder.freezed.dart';
+part 'folder.g.dart';
+
+@freezed
+sealed class SnCloudFolder with _$SnCloudFolder {
+  const factory SnCloudFolder({
+    required String id,
+    required String name,
+    required String? parentFolderId,
+    required String accountId,
+    required DateTime createdAt,
+    required DateTime updatedAt,
+  }) = _SnCloudFolder;
+
+  factory SnCloudFolder.fromJson(Map<String, dynamic> json) =>
+      _$SnCloudFolderFromJson(json);
+}