feat: K8s集群导出改为导出所有命名空间资源，去掉命名空间选择

- 后端: 新增 ExportResourcesAllNS handler (GET /:clusterCode/export)，遍历所有NS收集资源
- 前端: KubernetesClusters 导出弹窗去掉命名空间输入框，一键导出全部NS
- API: exportResources → exportAllResources，无需传 namespace 参数

frontend/src/services/api.ts

@@ -190,9 +190,9 @@ export const kubernetesApi = {
   syncCluster: async (clusterId: number | string) => {
     return http.post(`/kubernetes-clusters/${clusterId}/sync`);
   },
-  // 🆕 批量导出资源 (Deployment+Service+Ingress+ConfigMap+Secret) // Logan.Li
-  exportResources: async (clusterCode: string, namespace: string) => {
-    return http.download(`/kubernetes/${clusterCode}/namespace/${namespace}/export`, `${namespace}-resources.tar.gz`);
+  // 🆕 批量导出集群所有命名空间资源 // Logan.Li
+  exportAllResources: async (clusterCode: string) => {
+    return http.download(`/kubernetes/${clusterCode}/export`, `cluster-${clusterCode}-resources.tar.gz`);
   },
   getTopology: async (clusterId: number | string) => { // Logan.Li
     return http.get(`/kubernetes-clusters/${clusterId}/topology`);