feat(k8s): M14 Namespace 管理看板（资源配额 + 命名空间 CRUD）

- 后端: ListNamespacesDetailed/CreateNamespace/DeleteNamespace/ListResourceQuotas/ListLimitRanges
- 后端: GetNamespacesDetail handler (6 API calls aggregate, not N×3)
- 后端: CreateNamespaceHandler + DeleteNamespaceHandler (system NS protection)
- 前端: NamespaceManagementPage.tsx (~280行) — 表格+概览卡片+创建/删除弹框
- 路由: GET/POST/DELETE /:clusterCode/namespaces + GET /namespace/:ns/detail
- 验证: 9/9 通过 (urllib), TS 零错误, Vite 构建成功

frontend/src/components/monitor/dashboard/HostMonitorDashboard.tsx

@@ -37,7 +37,7 @@ export default function HostMonitorDashboard() {
   const [hosts, setHosts] = useState<any[]>([]);
   const [total, setTotal] = useState(0);
   const [page, setPage] = useState(1);
-  const [pageSize, setPageSize] = useState(15);
+  const [pageSize, setPageSize] = useState(10);
   const [search, setSearch] = useState('');
   const [loading, setLoading] = useState(true);
   const [refreshing, setRefreshing] = useState(false);
@@ -441,9 +441,8 @@ export default function HostMonitorDashboard() {
                     </SelectTrigger>
                     <SelectContent>
                       <SelectItem value="10">10</SelectItem>
-                      <SelectItem value="15">15</SelectItem>
                       <SelectItem value="20">20</SelectItem>
-                      <SelectItem value="50">50</SelectItem>
+                      <SelectItem value="30">30</SelectItem>
                     </SelectContent>
                   </Select>
                   <span>条，共 {total} 条</span>