feat: redesign admin panel with cyberpunk UI theme

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

panel/templates/login.html

@@ -3,7 +3,8 @@
 {% block body %}
 <div class="auth-wrap">
   <div class="auth-card">
-    <h1>jiedian 管理面板</h1>
+    <h1 class="auth-logo">jiedian</h1>
+    <p class="auth-subtitle">// secure access terminal</p>
     <p class="muted">登录后管理节点与分享链接</p>
     {% if error %}
     <div class="alert">{{ error }}</div>
@@ -13,7 +14,7 @@
       <input type="text" name="username" autocomplete="username" required autofocus>
       <label>密码</label>
       <input type="password" name="password" autocomplete="current-password" required>
-      <button type="submit" class="btn primary">登录</button>
+      <button type="submit" class="btn primary" style="width:100%;margin-top:20px;">登录</button>
     </form>
   </div>
 </div>