feat(ads): add native ad view abstraction

- Create an abstract NativeAdView widget to define the interface for rendering native ads
- This abstraction allows for provider-agnostic UI components and supports multiple ad network SDKs
- Concrete implementations will handle the actual rendering of native ad content

Author: fulleni

lib/ads/widgets/native_ad_view.dart

@@ -0,0 +1,22 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/models/native_ad.dart'
+    as app_native_ad;
+
+/// {@template native_ad_view}
+/// An abstract widget that defines the interface for rendering a native ad.
+///
+/// Concrete implementations of this widget will be responsible for displaying
+/// the native ad content from a specific ad network SDK (e.g., AdMob).
+/// This abstraction ensures that the higher-level UI components remain
+/// provider-agnostic.
+/// {@endtemplate}
+abstract class NativeAdView extends StatelessWidget {
+  /// {@macro native_ad_view}
+  const NativeAdView({required this.nativeAd, super.key});
+
+  /// The generic native ad data to display.
+  ///
+  /// This object contains the original, SDK-specific ad object, which concrete
+  /// implementations will cast and render.
+  final app_native_ad.NativeAd nativeAd;
+}