feat(ads): add native ad model

- Create a generic, provider-agnostic model for native advertisements
- Include common fields found in native ads
- Maintain a reference to the original, SDK-specific ad object
- Facilitate decoupling of application logic from specific ad network SDKs

Author: fulleni

lib/ads/models/native_ad.dart

@@ -0,0 +1,80 @@
+import 'package:equatable/equatable.dart';
+import 'package:flutter/foundation.dart';
+
+/// {@template native_ad}
+/// A generic, provider-agnostic model representing a native advertisement.
+///
+/// This model decouples the application's core logic from specific ad network
+/// SDKs (e.g., Google Mobile Ads). It contains common fields found in native
+/// ads and holds a reference to the original, SDK-specific ad object for
+/// rendering purposes.
+/// {@endtemplate}
+@immutable
+class NativeAd extends Equatable {
+  /// {@macro native_ad}
+  const NativeAd({
+    required this.id,
+    required this.headline,
+    required this.body,
+    required this.callToAction,
+    this.iconUrl,
+    this.imageUrl,
+    this.advertiser,
+    this.starRating,
+    this.store,
+    this.price,
+    required this.adObject,
+  });
+
+  /// A unique identifier for this specific native ad instance.
+  final String id;
+
+  /// The main headline or title of the advertisement.
+  final String headline;
+
+  /// The main body text or description of the advertisement.
+  final String body;
+
+  /// The text for the call-to-action button (e.g., "Install", "Learn More").
+  final String callToAction;
+
+  /// The URL of the ad's icon image (e.g., app icon).
+  final String? iconUrl;
+
+  /// The URL of the main image asset for the ad.
+  final String? imageUrl;
+
+  /// The name of the advertiser or sponsor.
+  final String? advertiser;
+
+  /// The star rating for the advertised app (typically 1.0 to 5.0).
+  final double? starRating;
+
+  /// The name of the app store (e.g., "Google Play", "App Store").
+  final String? store;
+
+  /// The price of the advertised app or product.
+  final String? price;
+
+  /// The original, SDK-specific ad object.
+  ///
+  /// This object is passed directly to the ad network's UI widget for rendering.
+  /// It should be cast back to its specific type (e.g., `google_mobile_ads.NativeAd`)
+  /// only within the dedicated ad rendering widget for that provider.
+  final Object adObject;
+
+  @override
+  List<Object?> get props => [
+        id,
+        headline,
+        body,
+        callToAction,
+        iconUrl,
+        imageUrl,
+        advertiser,
+        starRating,
+        store,
+        price,
+        adObject,
+      ];
+}