feat: 路由改名/kubectl预装/导出YAML精简/Service标签页优化/Alpine镜像源换清华

- 路由 /deploy/credentials → /deploy/configureTools
- kubectl 改为预装(Dockerfile) + 种子数据 preinstall
- 导出YAML精简: Service/Ingress/Deployment 全面清理运行时字段
- DeploymentEditService 只显示匹配 selector 的关联 Service
- Alpine 镜像源 mirrors.aliyun.com → mirrors.tuna.tsinghua.edu.cn

backend/internal/models/deploy_tool.go

@@ -66,9 +66,9 @@ func PredefinedTools() []DeployTool {
 		{
 			Name:           "kubectl",
 			DisplayName:    "Kubectl",
-			Description:    "Kubernetes 命令行工具，用于 K8s 集群交互",
+			Description:    "Kubernetes 命令行工具，用于 K8s 集群交互（已预装在镜像中）",
 			Category:       "k8s",
-			InstallMethod:  ToolLazy,
+			InstallMethod:  ToolPreinstall,
 			BinaryName:     "kubectl",
 			InstallPath:    "/usr/local/bin/kubectl",
 			CheckCommand:   "kubectl version --client --short 2>/dev/null || kubectl version --client 2>/dev/null",