feat(ads): implement interstitial ad trigger in headlines search

- Add InterstitialAdManager import to headlines_search_page.dart
- Implement interstitial ad trigger on headline tap for different image styles
- Maintain existing navigation to article details after ad trigger

Author: fulleni

lib/headlines-search/view/headlines_search_page.dart

@@ -6,6 +6,7 @@ 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';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/feed_ad_loader_widget.dart';
@@ -313,29 +314,44 @@ class _HeadlinesSearchViewState extends State<_HeadlinesSearchView> {
                             case HeadlineImageStyle.hidden:
                               tile = HeadlineTileTextOnly(
                                 headline: feedItem,
-                                onHeadlineTap: () => context.goNamed(
-                                  Routes.searchArticleDetailsName,
-                                  pathParameters: {'id': feedItem.id},
-                                  extra: feedItem,
-                                ),
+                                onHeadlineTap: () {
+                                  context
+                                      .read<InterstitialAdManager>()
+                                      .onPotentialAdTrigger(context: context);
+                                  context.goNamed(
+                                    Routes.searchArticleDetailsName,
+                                    pathParameters: {'id': feedItem.id},
+                                    extra: feedItem,
+                                  );
+                                },
                               );
                             case HeadlineImageStyle.smallThumbnail:
                               tile = HeadlineTileImageStart(
                                 headline: feedItem,
-                                onHeadlineTap: () => context.goNamed(
-                                  Routes.searchArticleDetailsName,
-                                  pathParameters: {'id': feedItem.id},
-                                  extra: feedItem,
-                                ),
+                                onHeadlineTap: () {
+                                  context
+                                      .read<InterstitialAdManager>()
+                                      .onPotentialAdTrigger(context: context);
+                                  context.goNamed(
+                                    Routes.searchArticleDetailsName,
+                                    pathParameters: {'id': feedItem.id},
+                                    extra: feedItem,
+                                  );
+                                },
                               );
                             case HeadlineImageStyle.largeThumbnail:
                               tile = HeadlineTileImageTop(
                                 headline: feedItem,
-                                onHeadlineTap: () => context.goNamed(
-                                  Routes.searchArticleDetailsName,
-                                  pathParameters: {'id': feedItem.id},
-                                  extra: feedItem,
-                                ),
+                                onHeadlineTap: () {
+                                  context
+                                      .read<InterstitialAdManager>()
+                                      .onPotentialAdTrigger(context: context);
+                                  context.goNamed(
+                                    Routes.searchArticleDetailsName,
+                                    pathParameters: {'id': feedItem.id},
+                                    extra: feedItem,
+                                  );
+                                },
                               );
                           }
                           return tile;