fix: 登录状态检查改为手动触发，避免自动请求不断弹出浏览器窗口

- useLoginStatus 默认 auto=false，不再挂载时自动请求
- Dashboard 登录状态卡片改为 "Click to check" 手动触发
- Login 页面初始显示 "Click Refresh to check" 提示
- Header 添加 Token 未配置警告横幅，引导用户去 Settings

web/src/pages/DashboardPage.tsx

@@ -9,7 +9,7 @@ import { useNavigate } from 'react-router-dom';
 
 export function DashboardPage() {
   const { health, loading: healthLoading, refresh: refreshHealth } = useHealth(10_000);
-  const { status: loginStatus, loading: loginLoading } = useLoginStatus();
+  const { status: loginStatus, loading: loginLoading, refresh: refreshLogin } = useLoginStatus();
   const navigate = useNavigate();
 
   return (
@@ -65,7 +65,12 @@ export function DashboardPage() {
               )}
             </div>
           ) : (
-            <Badge variant="warning">Unknown</Badge>
+            <button
+              onClick={() => void refreshLogin()}
+              className="text-xs text-dark-accent hover:underline"
+            >
+              Click to check
+            </button>
           )}
         </Card>