feat: add arch

lib/core/utils/app_exceptions.dart

@@ -0,0 +1,21 @@
+class AppException implements Exception {
+  final String message;
+  final String prefix;
+
+  AppException([this.message = 'An unknown error occurred.', this.prefix = '']);
+
+  @override
+  String toString() {
+    return '$prefix$message';
+  }
+}
+
+class FetchDataException extends AppException {
+  FetchDataException([String? message])
+    : super(message ?? 'Error During Communication: ', 'Network Error');
+}
+
+class AuthenticationException extends AppException {
+  AuthenticationException([String? message])
+    : super(message ?? 'Authentication Failed.', 'Auth Error');
+}