fix(chat): remove dynamic upgradeHint for daily limit message

src/app/chat/chat-screen.tsx

@@ -48,8 +48,7 @@ export function ChatScreen() {
   // 消息数量限制由后端统一返回 lockDetail，前端不再处理本地额度。
   const showMessageLimitBanner =
     state.upgradePromptVisible && state.upgradeReason === "daily_limit";
-  const messageLimitTitle =
-    state.upgradeHint ?? "The limit for free chat times\nhas been reached";
+  const messageLimitTitle = "The limit for free chat times\nhas been reached";
   const messageLimitCta = isGuest ? "Log in to continue chatting" : undefined;
 
   const showPrivatePaywallBanner =

src/stores/chat/chat-machine.helpers.ts

@@ -157,7 +157,7 @@ export function applyHttpSendOutput(
       isReplyingAI: false,
       upgradePromptVisible: true,
       upgradeReason: "daily_limit",
-      upgradeHint: lockDetail.hint,
+      upgradeHint: null,
       upgradeDetail: normalizeLockDetail(lockDetail.detail),
     };
   }