refactor(headlines-search): improve ad caching and remove unused imports

- Inject InlineAdCacheService into HeadlinesSearchBloc
- Replace InlineAdCacheService instantiation with injected service
- Remove unused AdService import from headlines_search_page.dart
- Update ad loading to use FeedAdLoaderWidget without explicit AdService

Author: fulleni

lib/headlines-search/bloc/headlines_search_bloc.dart

@@ -22,12 +22,14 @@ class HeadlinesSearchBloc
     required DataRepository<Country> countryRepository,
     required AppBloc appBloc,
     required FeedDecoratorService feedDecoratorService,
+    required InlineAdCacheService inlineAdCacheService,
   }) : _headlinesRepository = headlinesRepository,
        _topicRepository = topicRepository,
        _sourceRepository = sourceRepository,
        _countryRepository = countryRepository,
        _appBloc = appBloc,
        _feedDecoratorService = feedDecoratorService,
+       _inlineAdCacheService = inlineAdCacheService,
        super(const HeadlinesSearchInitial()) {
     on<HeadlinesSearchModelTypeChanged>(_onHeadlinesSearchModelTypeChanged);
     on<HeadlinesSearchFetchRequested>(
@@ -42,6 +44,7 @@ class HeadlinesSearchBloc
   final DataRepository<Country> _countryRepository;
   final AppBloc _appBloc;
   final FeedDecoratorService _feedDecoratorService;
+  final InlineAdCacheService _inlineAdCacheService;
   static const _limit = 10;
 
   Future<void> _onHeadlinesSearchModelTypeChanged(
@@ -201,7 +204,7 @@ class HeadlinesSearchBloc
     }
 
     // New search, clear previous ad cache.
-    InlineAdCacheService().clearAllAds();
+    _inlineAdCacheService.clearAllAds();
     emit(
       HeadlinesSearchLoading(
         lastSearchTerm: searchTerm,

lib/headlines-search/view/headlines_search_page.dart

@@ -5,7 +5,6 @@
 import 'package:core/core.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
-import 'package:flutter_news_app_mobile_client_full_source_code/ads/ad_service.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/interstitial_ad_manager.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/ad_placeholder.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/ad_theme_style.dart';
@@ -365,7 +364,6 @@ class _HeadlinesSearchViewState extends State<_HeadlinesSearchView> {
 
                           return FeedAdLoaderWidget(
                             adPlaceholder: feedItem,
-                            adService: context.read<AdService>(),
                             adThemeStyle: AdThemeStyle.fromTheme(
                               Theme.of(context),
                             ),