feat: 内置演示账号 demo/demo1234 + 登录页一键填充 + 服务器地址修复

app/src/components/auth/LoginPage.tsx

@@ -29,10 +29,10 @@ export function LoginPage() {
     setError('');
     try {
       if (mode === 'login') {
-        await serverLogin(username.trim(), password);
+        await serverLogin(username.trim(), password, serverUrl);
       } else {
         if (!invite.trim()) throw new Error('请填写邀请码');
-        await serverRegister(username.trim(), password, invite.trim());
+        await serverRegister(username.trim(), password, invite.trim(), serverUrl);
       }
       setTimeout(() => window.location.reload(), 200);
     } catch (e) {
@@ -87,7 +87,13 @@ export function LoginPage() {
           <Button variant="primary" size="lg" onClick={() => void submit()} disabled={busy}>
             {busy ? '请稍候…' : (mode === 'login' ? '进入我的档案' : '创建我的档案')}
           </Button>
-          <p className="text-center text-[11px] text-ink-3">数据按账号隔离存储 · 未注册用户请联系管理员获取邀请码</p>
+          <button
+            type="button"
+            className="mt-1 flex w-full items-center justify-center gap-1.5 rounded-md border border-dashed border-line px-3 py-2 text-[11.5px] text-ink-3 transition-colors hover:border-brand/40 hover:text-brand-text"
+            onClick={() => { setUsername('demo'); setPassword('demo1234'); }}
+          >
+            演示账号：demo / demo1234（点击填充）
+          </button>
         </div>
       </div>
     </div>