feat: refund page

lib/presentation/refund/bloc/refund_state.dart

@@ -0,0 +1,9 @@
+part of 'refund_bloc.dart';
+
+@freezed
+class RefundState with _$RefundState {
+  const factory RefundState.initial() = _Initial;
+  const factory RefundState.loading() = _Loading;
+  const factory RefundState.success() = _Success;
+  const factory RefundState.error(String message) = _Error;
+}