feat(ads): 네이티브 광고 적용 및 디버그 스위치 이동

lib/core/constants/app_constants.dart

@@ -19,6 +19,14 @@ class AppConstants {
   static const String iosAdAppId = 'ca-app-pub-3940256099942544~1458002511';
   static const String interstitialAdUnitId =
       'ca-app-pub-3940256099942544/1033173712';
+  static const String androidNativeAdUnitId =
+      'ca-app-pub-6691216385521068/7939870622';
+  static const String iosNativeAdUnitId =
+      'ca-app-pub-6691216385521068/7939870622';
+  static const String testAndroidNativeAdUnitId =
+      'ca-app-pub-3940256099942544/2247696110';
+  static const String testIosNativeAdUnitId =
+      'ca-app-pub-3940256099942544/3986624511';
 
   // Hive Box Names
   static const String restaurantBox = 'restaurants';

lib/core/utils/ad_helper.dart

@@ -0,0 +1,28 @@
+import 'package:flutter/foundation.dart';
+
+import '../constants/app_constants.dart';
+
+class AdHelper {
+  static bool get isMobilePlatform {
+    if (kIsWeb) return false;
+    return defaultTargetPlatform == TargetPlatform.android ||
+        defaultTargetPlatform == TargetPlatform.iOS;
+  }
+
+  static String get nativeAdUnitId {
+    if (!isMobilePlatform) {
+      throw UnsupportedError('Native ads are only supported on mobile.');
+    }
+
+    final isIOS = defaultTargetPlatform == TargetPlatform.iOS;
+    if (isIOS) {
+      if (kDebugMode) {
+        return AppConstants.testIosNativeAdUnitId;
+      }
+      return AppConstants.iosNativeAdUnitId;
+    }
+
+    // Android는 디버그/릴리즈 모두 실제 광고 단위 ID 사용
+    return AppConstants.androidNativeAdUnitId;
+  }
+}