refactor(ads): enhance InArticleAdLoaderWidget for demo environment

- Add support for displaying placeholder ads in demo environment
- Integrate DemoBannerAdWidget and DemoNativeAdWidget for demo mode
- Update ad loading logic for different environments
- Improve error handling and fallback to SizedBox.shrink()

Author: fulleni

lib/ads/widgets/in_article_ad_loader_widget.dart

@@ -10,10 +10,12 @@ import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/banne
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/inline_ad.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/native_ad.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/admob_inline_ad_widget.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/demo_banner_ad_widget.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/demo_native_ad_widget.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/local_banner_ad_widget.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/local_native_ad_widget.dart';
-import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/placeholder_ad_widget.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/app/bloc/app_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/app/config/app_environment.dart';
 import 'package:logging/logging.dart';
 import 'package:ui_kit/ui_kit.dart';
 
@@ -208,6 +210,33 @@ class _InArticleAdLoaderWidgetState extends State<InArticleAdLoaderWidget> {
 
   @override
   Widget build(BuildContext context) {
+    final appEnvironment = context.read<AppBloc>().state.environment;
+    final headlineImageStyle = context
+        .read<AppBloc>()
+        .state
+        .settings
+        .feedPreferences
+        .headlineImageStyle;
+
+    // In demo environment, display placeholder ads directly.
+    if (appEnvironment == AppEnvironment.demo) {
+      // Determine the ad type from the adConfig's articleAdConfiguration
+      final adType =
+          widget.adConfig.articleAdConfiguration.defaultInArticleAdType;
+      switch (adType) {
+        case AdType.native:
+          return DemoNativeAdWidget(headlineImageStyle: headlineImageStyle);
+        case AdType.banner:
+          return DemoBannerAdWidget(headlineImageStyle: headlineImageStyle);
+        case AdType.interstitial:
+        case AdType.video:
+          // Interstitial and video ads are not inline, so they won't be
+          // handled by InArticleAdLoaderWidget. Fallback to a generic placeholder.
+          return const SizedBox.shrink();
+      }
+    }
+
+    // For other environments (development, production), proceed with real ad loading.
     if (_isLoading) {
       return const Padding(
         padding: EdgeInsets.symmetric(
@@ -222,26 +251,31 @@ class _InArticleAdLoaderWidgetState extends State<InArticleAdLoaderWidget> {
         ),
       );
     } else if (_hasError || _loadedAd == null) {
-      return const PlaceholderAdWidget();
+      return const SizedBox.shrink();
     } else {
       // If an ad is successfully loaded, dispatch to the appropriate
       // provider-specific widget for rendering.
       switch (_loadedAd!.provider) {
         case AdPlatformType.admob:
-          return AdmobInlineAdWidget(inlineAd: _loadedAd!);
+          return AdmobInlineAdWidget(
+            inlineAd: _loadedAd!,
+            headlineImageStyle: headlineImageStyle,
+          );
         case AdPlatformType.local:
           if (_loadedAd is NativeAd && _loadedAd!.adObject is LocalNativeAd) {
             return LocalNativeAdWidget(
               localNativeAd: _loadedAd!.adObject as LocalNativeAd,
+              headlineImageStyle: headlineImageStyle,
             );
           } else if (_loadedAd is BannerAd &&
               _loadedAd!.adObject is LocalBannerAd) {
             return LocalBannerAdWidget(
               localBannerAd: _loadedAd!.adObject as LocalBannerAd,
+              headlineImageStyle: headlineImageStyle,
             );
           }
           // Fallback for unsupported local ad types or errors
-          return const PlaceholderAdWidget();
+          return const SizedBox.shrink();
       }
     }
   }