fix: remove default admin username from login form

Co-authored-by: Cursor <cursoragent@cursor.com>

web/dist/index.html

@@ -81,7 +81,7 @@
         <div class="tile login-card">
           <div class="settings-title">登录</div>
           <label class="field"><span class="label">用户名</span>
-            <input id="loginUser" class="field-input" value="admin" autocomplete="username" />
+            <input id="loginUser" class="field-input" value="" autocomplete="username" placeholder="请输入用户名" />
           </label>
           <label class="field"><span class="label">密码</span>
             <input id="loginPass" type="password" class="field-input" autocomplete="current-password" />

web/src/components/LoginGate.tsx

@@ -6,7 +6,7 @@ type Props = {
 };
 
 export default function LoginGate({ onOk }: Props) {
-  const [username, setUsername] = useState("admin");
+  const [username, setUsername] = useState("");
   const [password, setPassword] = useState("");
   const [err, setErr] = useState<string | null>(null);
   const [busy, setBusy] = useState(false);
@@ -39,6 +39,7 @@ export default function LoginGate({ onOk }: Props) {
             value={username}
             onChange={(e) => setUsername(e.target.value)}
             autoComplete="username"
+            placeholder="请输入用户名"
             autoFocus
           />
         </label>