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/components/layout/Header.tsx

@@ -1,12 +1,29 @@
 import { useHealth } from '@/hooks/useHealth';
+import { useAuth } from '@/context/AuthContext';
 import { Badge } from '@/components/ui/Badge';
+import { useNavigate } from 'react-router-dom';
 
 export function Header() {
   const { health } = useHealth(15_000);
+  const { token } = useAuth();
+  const navigate = useNavigate();
 
   return (
     <header className="h-14 bg-dark-card border-b border-dark-border flex items-center justify-between px-6 shrink-0">
-      <div />
+      <div>
+        {!token && (
+          <button
+            onClick={() => navigate('/settings')}
+            className="flex items-center gap-2 px-3 py-1.5 rounded-lg bg-dark-warning/15 border border-dark-warning/30 text-dark-warning text-xs font-medium hover:bg-dark-warning/25 transition-colors"
+          >
+            <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+              <path d="M10.29 3.86L1.82 18a2 2 0 0 0 1.71 3h16.94a2 2 0 0 0 1.71-3L13.71 3.86a2 2 0 0 0-3.42 0z" />
+              <line x1="12" y1="9" x2="12" y2="13" /><line x1="12" y1="17" x2="12.01" y2="17" />
+            </svg>
+            Token 未配置 — 点击前往 Settings
+          </button>
+        )}
+      </div>
       <div className="flex items-center gap-3">
         {health && (
           <Badge variant={health.healthy ? 'success' : 'danger'}>