feat: Implement initial authentication, multi-environment support, and core app infrastructure.

lib/features/auth/data/models/user_model.dart

@@ -0,0 +1,19 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'user_model.freezed.dart';
+part 'user_model.g.dart';
+
+@freezed
+abstract class UserModel with _$UserModel {
+  const factory UserModel({
+    required String id,
+    required String email,
+    required String role,
+    String? firstName,
+    String? lastName,
+    String? avatar,
+  }) = _UserModel;
+
+  factory UserModel.fromJson(Map<String, dynamic> json) =>
+      _$UserModelFromJson(json);
+}