refactor: 全局重命名 k8s → kubernetes (前后端+路由+表名+文件)

后端:
  - pkg/k8sclient → pkg/kubernetesclient
  - models/k8s.go → models/kubernetes.go
  - handlers/k8s.go → handlers/kubernetes.go
  - K8sCluster/K8sNode/.. → KubernetesCluster/KubernetesNode/..
  - K8sHandler → KubernetesHandler
  - 路由: /k8s-clusters → /kubernetes-clusters
  - 路由: /k8s/:code/namespace/:ns/... → /kubernetes/:code/namespace/:ns/... (Kuboard风格)
  - 表前缀: container_k8s_ → container_kubernetes_

前端:
  - components/k8s/ → components/kubernetes/
  - K8sClusters → KubernetesClusters
  - K8sWorkloads → KubernetesWorkloads
  - K8sNodes → KubernetesNodes
  - k8sApi → kubernetesApi
  - 路由前缀: /k8s/ → /kubernetes/

测试验证:
✅ /kubernetes/k8s-cluster-liren/namespace/kube-system/deployments → 3 items
✅ /kubernetes/k8s-cluster-liren/namespace/kube-system/pods → 7 items
✅ /kubernetes/k8s-cluster-liren/namespace/kube-system/services → 4 items
✅ /kubernetes/k8s-cluster-liren/namespace/kube-system/configmaps → 6 items
✅ /kubernetes/k8s-cluster-liren/namespace/kube-system/secrets → 1 item
✅ /kubernetes/k8s-cluster-liren/namespaces → 4 items

backend/internal/api/handlers/audit.go

@@ -134,7 +134,7 @@ func (h *AuditHandler) GetAuditModules(c *gin.Context) {
 	modules := []map[string]string{
 		{"value": "user", "label": "用户管理"},
 		{"value": "server", "label": "服务器管理"},
-		{"value": "k8s", "label": "Kubernetes"},
+		{"value": "kubernetes", "label": "Kubernetes"},
 		{"value": "alert", "label": "监控告警"},
 		{"value": "pipeline", "label": "应用发布"},
 		{"value": "automation", "label": "自动化运维"},