fix(ios): resolve native asset registration issues in New Architecture

This commit fixes an issue where native ad assets could not be found via their react tags when the New Architecture (Fabric) was enabled.

- Added a recursive findViewByTag:inView: helper method to navigate the view hierarchy.
- Updated registerAsset:reactTag: to use the new lookup logic in New Architecture.
- The lookup now searches within both the _nativeAdView and the component itself.

Author: 이명규

ios/RNGoogleMobileAds/RNGoogleMobileAdsNativeView.mm

@@ -104,6 +104,23 @@ - (void)handleCommand:(const NSString *)commandName args:(const NSArray *)args {
   RCTRNGoogleMobileAdsNativeViewHandleCommand(self, commandName, args);
 }
 
+- (UIView *)findViewByTag:(NSInteger)targetTag inView:(UIView *)parentView {
+  for (UIView *subview in parentView.subviews) {
+    if (subview.tag == targetTag) {
+      return subview;
+    }
+    if ([subview isKindOfClass:[RCTViewComponentView class]]) {
+      UIView *contentView = ((RCTViewComponentView *)subview).contentView;
+      if (contentView && contentView.tag == targetTag) {
+        return contentView;
+      }
+    }
+    UIView *found = [self findViewByTag:targetTag inView:subview];
+    if (found) return found;
+  }
+  return nil;
+}
+
 #else
 #pragma mark - Paper specific
 
@@ -128,7 +145,14 @@ - (void)setResponseId:(NSString *)responseId {
 
 - (void)registerAsset:(NSString *)assetType reactTag:(NSInteger)reactTag {
   RCTExecuteOnMainQueue(^{
+#ifdef RCT_NEW_ARCH_ENABLED
+    UIView *view = [self findViewByTag:reactTag inView:_nativeAdView];
+    if (!view) {
+      view = [self findViewByTag:reactTag inView:self];
+    }
+#else
     UIView *view = [_bridge.uiManager viewForReactTag:@(reactTag)];
+#endif
     if (!view) {
       RCTLogError(@"Cannot find NativeAssetView with tag #%zd while registering asset type %@",
                   reactTag, assetType);