feat(ads): add native ad template type

- Introduce NativeAdTemplateType enum to define visual templates for native ads
- Add templateType property to NativeAd class
- Update NativeAd props to include templateType
- Improve documentation for ad-related classes and enums

Author: fulleni

lib/ads/models/native_ad.dart

@@ -1,6 +1,20 @@
 import 'package:equatable/equatable.dart';
 import 'package:flutter/foundation.dart';
 
+/// {@template native_ad_template_type}
+/// Defines the visual template type for a native ad.
+///
+/// This is used to determine the expected size and layout of the native ad
+/// when rendering it in the UI.
+/// {@endtemplate}
+enum NativeAdTemplateType {
+  /// A small native ad template, typically used for compact layouts.
+  small,
+
+  /// A medium native ad template, typically used for more prominent layouts.
+  medium,
+}
+
 /// {@template ad_provider_type}
 /// Defines the supported ad network providers.
 ///
@@ -11,7 +25,7 @@ enum AdProviderType {
   /// Google AdMob provider.
   admob,
 
-  /// A placeholder provider for platforms where native ads are not supported.
+  /// A placeholder provider for platforms where native ad SDKs are not supported.
   ///
   /// This is primarily used for the web demo environment to maintain UI
   /// consistency without relying on native SDKs.
@@ -33,6 +47,7 @@ class NativeAd extends Equatable {
     required this.id,
     required this.provider,
     required this.adObject,
+    required this.templateType,
   });
 
   /// A unique identifier for this specific native ad instance.
@@ -50,6 +65,9 @@ class NativeAd extends Equatable {
   /// only within the dedicated ad rendering widget for that provider.
   final Object adObject;
 
+  /// The template type of the native ad, indicating its expected size and layout.
+  final NativeAdTemplateType templateType;
+
   @override
-  List<Object?> get props => [id, provider, adObject];
+  List<Object?> get props => [id, provider, adObject, templateType];
 }