fix(chat): 채팅 쿼터 구매 동선을 정리한다

SodaLive/Sources/Chat/Talk/Room/ChatRoomViewModel.swift

@@ -279,9 +279,16 @@ final class ChatRoomViewModel: ObservableObject {
 
     func showRewardedAdForChatQuota() {
         _Concurrency.Task {
-            await YandexRewardedAdManager.shared.showAdIfAvailable(for: .chatRoomQuota) { [weak self] in
+            let isShown = await YandexRewardedAdManager.shared.showAdIfAvailable(for: .chatRoomQuota) { [weak self] in
                 self?.purchaseChatQuota(chargeType: .ad, canOption: nil)
             }
+
+            if !isShown {
+                await MainActor.run {
+                    errorMessage = I18n.Chat.Room.rewardedAdLoadFailed
+                    isShowPopup = true
+                }
+            }
         }
     }