feat: 选题管理页面添加统一卡片容器，包裹标题、按钮、筛选和列表，视觉更整体

platform/frontend/index.html

@@ -89,7 +89,7 @@
               </div>
             </div>
           </div>
-          <div v-if="currentPage === 'topics'" style="margin-left: 160px; width: 100%; max-width: calc(100vw - 160px); padding: 0 20px; box-sizing: border-box; overflow-x: auto;">
+          <div v-if="currentPage === 'topics'" style="margin-left: 160px; width: 100%; max-width: calc(100vw - 160px); box-sizing: border-box; overflow-x: auto;">
             <div class="flex justify-between items-center mb-6" style="width: 100%;"><h2 class="text-2xl font-bold text-gray-800">📋 选题管理</h2></div>
             <div class="card mb-6" style="display: inline-block; min-width: fit-content;"><div class="flex flex-wrap gap-2 items-center">
               <el-button type="primary" size="small" @click="refreshAll">🔄 批量刷新</el-button>
@@ -131,6 +131,7 @@
               </el-table>
             </div>
           </div>
+        </div>
           <div v-if="currentPage === 'logs'">
             <h2 class="text-2xl font-bold mb-6 text-gray-800">📄 系统日志</h2>
             <div class="card">
@@ -156,6 +157,7 @@
               </el-table>
             </div>
           </div>
+        </div>
         </main>
       </div>
       <div v-if="loadingOverlay" class="loading-overlay"><el-spinner type="spinning" :size="50"></el-spinner><p class="ml-4 text-lg">{{ loadingText }}</p></div>