fix(router): resolve import path issue and update observer registration

- Remove relative import path for go_router_observer.dart
- Add absolute import path for go_router_observer.dart
- Ensure GoRouterObserver is correctly imported and used in the Router

Author: fulleni

lib/router/router.dart

@@ -2,7 +2,6 @@ import 'package:auth_repository/auth_repository.dart';
 import 'package:core/core.dart' hide AppStatus;
 import 'package:data_repository/data_repository.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_news_app_mobile_client_full_source_code/router/go_router_observer.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/account/view/account_page.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/account/view/manage_followed_items/countries/add_country_to_follow_page.dart';
@@ -38,6 +37,7 @@ import 'package:flutter_news_app_mobile_client_full_source_code/headlines-feed/v
 import 'package:flutter_news_app_mobile_client_full_source_code/headlines-search/bloc/headlines_search_bloc.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/headlines-search/view/headlines_search_page.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/l10n/l10n.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/router/go_router_observer.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/router/routes.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/settings/bloc/settings_bloc.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/settings/view/appearance_settings_page.dart';