refactor:flutter_news_app_api_server_full_source_code: update imports in response helper

- Replace `ht_api` and `ht_shared` imports with `core` package
- Update `request_id` import path

Author: fulleni

lib/src/helpers/response_helper.dart

@@ -1,8 +1,8 @@
 import 'dart:io';
 
+import 'package:core/core.dart';
 import 'package:dart_frog/dart_frog.dart';
-import 'package:ht_api/src/models/request_id.dart';
-import 'package:ht_shared/ht_shared.dart';
+import 'package:flutter_news_app_api_server_full_source_code/src/models/request_id.dart';
 
 /// A utility class to simplify the creation of standardized API responses.
 abstract final class ResponseHelper {