chore: initial release

lib/core/models/folder.dart

@@ -0,0 +1,41 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'folder.freezed.dart';
+part 'folder.g.dart';
+
+// Timestamp converter for Unix timestamps
+class TimestampConverter implements JsonConverter<DateTime, dynamic> {
+  const TimestampConverter();
+
+  @override
+  DateTime fromJson(dynamic json) {
+    if (json is String) {
+      return DateTime.parse(json);
+    } else if (json is int) {
+      return DateTime.fromMillisecondsSinceEpoch(json * 1000);
+    } else {
+      throw ArgumentError('Invalid date format: $json');
+    }
+  }
+
+  @override
+  dynamic toJson(DateTime object) {
+    return object.millisecondsSinceEpoch ~/ 1000;
+  }
+}
+
+@freezed
+sealed class Folder with _$Folder {
+  const factory Folder({
+    required String id,
+    required String name,
+    @TimestampConverter() required DateTime createdAt,
+    @TimestampConverter() required DateTime updatedAt,
+    String? parentId,
+    @Default([]) List<String> conversationIds,
+    @Default([]) List<Folder> subfolders,
+    @Default({}) Map<String, dynamic> metadata,
+  }) = _Folder;
+
+  factory Folder.fromJson(Map<String, dynamic> json) => _$FolderFromJson(json);
+}