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

frontend/src/components/dashboard/Dashboard.tsx

@@ -1,7 +1,7 @@
 import { useCallback, useEffect, useState } from 'react';
 import { Button } from '@/components/ui/button';
 import { Clock, Server, Cloud, Bell, DollarSign } from 'lucide-react';
-import { dashboardStatsApi, serverApi, k8sApi } from '@/services/api';
+import { dashboardStatsApi, serverApi, kubernetesApi } from '@/services/api';
 import { StatCard } from './DashboardStats';
 import { CostOverviewCard, TopResourceUsageCard, ResourceUsageCard, computeMonthChange } from './DashboardCharts';
 import {
@@ -9,7 +9,7 @@ import {
   CertificateExpiryCard,
   ReleaseHistoryCard,
   ServerStatusCard,
-  K8sClusterCard,
+  KubernetesClusterCard,
 } from './DashboardRecent';
 
 export function Dashboard() {
@@ -35,7 +35,7 @@ export function Dashboard() {
           console.error('Failed to fetch servers:', e);
           return null;
         }),
-        k8sApi.getClusters().catch((e) => {
+        kubernetesApi.getClusters().catch((e) => {
           console.error('Failed to fetch k8s clusters:', e);
           return null;
         }),
@@ -82,7 +82,7 @@ export function Dashboard() {
   }
 
   const serverStats = stats?.server_stats;
-  const k8sStats = stats?.k8s_stats;
+  const k8sStats = stats?.kubernetes_stats;
   const alertStats = stats?.alert_stats;
   const costStats = stats?.cost_stats;
   const costChange = computeMonthChange(costStats?.month_trend);
@@ -165,7 +165,7 @@ export function Dashboard() {
       <div className="grid grid-cols-1 lg:grid-cols-3 gap-6">
         <ReleaseHistoryCard releases={releases} />
         <ServerStatusCard servers={servers} />
-        <K8sClusterCard clusters={clusters} />
+        <KubernetesClusterCard clusters={clusters} />
       </div>
     </div>
   );