refactor(ads): move demo environment ad logic to correct platform type

- Remove app environment check from build method
- Remove unused import of AppEnvironment
- Move demo environment ad logic to AdPlatformType case statement
- Simplify ad loading logic for non-demo environments

Author: fulleni

lib/ads/widgets/feed_ad_loader_widget.dart

@@ -16,7 +16,6 @@ import 'package:flutter_news_app_mobile_client_full_source_code/ads/widgets/demo
 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/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';
 
@@ -263,30 +262,13 @@ class _FeedAdLoaderWidgetState extends State<FeedAdLoaderWidget> {
 
   @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) {
-      switch (widget.adPlaceholder.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 FeedAdLoaderWidget. Fallback to a generic placeholder.
-          return const SizedBox.shrink();
-      }
-    }
-
-    // For other environments (development, production), proceed with real ad loading.
     if (_isLoading) {
       // Show a shimmer or loading indicator while the ad is being loaded.
       return const Padding(
@@ -302,7 +284,7 @@ class _FeedAdLoaderWidgetState extends State<FeedAdLoaderWidget> {
         ),
       );
     } else if (_hasError || _loadedAd == null) {
-      // Fallback for unsupported local ad types or errors
+      // Fallback for unsupported ad types or errors
       return const SizedBox.shrink();
     } else {
       // If an ad is successfully loaded, dispatch to the appropriate
@@ -328,6 +310,19 @@ class _FeedAdLoaderWidgetState extends State<FeedAdLoaderWidget> {
           }
           // Fallback for unsupported local ad types or errors
           return const SizedBox.shrink();
+        case AdPlatformType.demo:
+          // In demo environment, display placeholder ads directly.
+          switch (widget.adPlaceholder.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 FeedAdLoaderWidget. Fallback to a generic placeholder.
+              return const SizedBox.shrink();
+          }
       }
     }
   }