fix: 删除重复的导出/导入/退出元素

- 之前正则替换失败导致两套 header 元素
- 手动删除重复的 export/import/退出
- 现在只有一套正确的导航栏

frontend/index.html

@@ -393,27 +393,6 @@ body{font-family:-apple-system,BlinkMacSystemFont,"SF Pro Display","SF Pro Text"
       <a href="#" class="logout-link" onclick="doLogout()">退出</a>
     </div>
   </div>
-</div>
-      </div>
-      <div class="export-wrap">
-        <button class="hdr-btn" onclick="toggleExport(event)">导出</button>
-        <div class="export-menu" id="exportMenu">
-          <a href="#" onclick="exportCSV(event)">导出 CSV</a>
-          <a href="#" onclick="exportJSON(event)">导出 JSON</a>
-          <a href="#" onclick="exportHTML(event)">导出 HTML</a>
-        </div>
-      </div>
-      <div class="export-wrap">
-        <button class="hdr-btn" onclick="toggleImport(event)">导入</button>
-        <div class="export-menu" id="importMenu">
-          <a href="#" onclick="downloadTemplate(event)">下载模板</a>
-          <a href="#" onclick="showImportModal(event)">导入 CSV</a>
-        </div>
-      </div>
-      <a href="/admin.html" class="admin-link" id="adminLink" style="display:none">管理</a>
-      <a href="#" class="logout-link" onclick="doLogout()">退出</a>
-    </div>
-  </div>
 </div>
 <div class="main">
   <div style="display:flex;flex-direction:column;gap:16px">