fix(chat): use weekly limit for message quota

src/app/chat/chat-screen.tsx

@@ -44,7 +44,7 @@ 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";
+    state.upgradePromptVisible && state.upgradeReason === "weekly_limit";
   const messageLimitTitle = "The limit for free chat times\nhas been reached";
 
   const externalBrowserPromptShownRef = useRef(false);

src/app/chat/components/chat-quota-exhausted-banner.tsx

@@ -3,7 +3,7 @@
  * ChatQuotaExhaustedBanner 游客配额耗尽横幅
  *
  * 何时显示：
- *   - 后端返回 lockDetail.reason="daily_limit" 且 showUpgrade=true
+ *   - 后端返回 lockDetail.reason="weekly_limit" 且 showUpgrade=true
  *
  * 视觉规格（与设计稿对齐）：
  *   - 粉→品红渐变背景（与 splash 渐变一致）