fix lan switch

api/templates/index.html

@@ -48,11 +48,14 @@
                 </ul>
                 
                 <ul class="navbar-nav mb-2 mb-lg-0">
-                    <li class="nav-item">
-                        <button class="nav-link active" aria-current="page" set-lan="html:en" onclick="changeLan(this)" value="en">英文</button>
-                    </li>
-                    <li class="nav-item">
-                        <button class="nav-link active" aria-current="page" set-lan="html:zh" onclick="changeLan(this)" value="zh">中文</button>
+                    <li class="nav-item dropdown">
+                        <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
+                            中/En
+                        </a>
+                        <ul class="dropdown-menu" aria-labelledby="navbarDropdown">
+                            <li><button class="nav-link lan-swtich" aria-current="page" set-lan="html:en" onclick="changeLan(this)" value="en">English</button></li>
+                            <li><button class="nav-link lan-switch" aria-current="page" set-lan="html:zh" onclick="changeLan(this)" value="zh">中文</button></li>
+                        </ul>
                     </li>
                     <li class="nav-item">
                         <a class="nav-link active" aria-current="page" href="/login" set-lan="html:login">登入</a>