feat: K8s 集群实时代理 — 直接调用 K8s API 不存储 MySQL

- 新增 pkg/k8sclient 轻量级 K8s REST 客户端（解析 kubeconfig TLS 证书）
- ListNodes/Pods/Deployments/Services/Ingresses 改为实时代理 K8s API
- 集群同步端点 POST /:id/sync（拉取后仍存 MySQL 用于离线缓存储备）
- 前端 k8sApi 新增 syncCluster 方法
- 修复 SNMP MaxRepetitions uint8→uint32 类型错误
- 修复 ServicePort.TargetPort 兼容 int/string 双类型
- 创建 k8s_nodes/pods/deployments/services/ingresses 五张表

backend/internal/api/routes/routes.go

@@ -239,6 +239,7 @@ func Register(r *gin.Engine, db *gorm.DB, log *zap.Logger, cfg *config.Config, c
 		clusters.POST("", k8sHandler.CreateCluster)
 		clusters.PUT("/:id", k8sHandler.UpdateCluster)
 		clusters.DELETE("/:id", k8sHandler.DeleteCluster)
+		clusters.POST("/:id/sync", k8sHandler.SyncCluster) // 同步集群资源 // Logan.Li
 		clusters.GET("/:id/nodes", k8sHandler.ListNodes)
 		clusters.GET("/:id/pods", k8sHandler.ListPods)
 		clusters.GET("/:id/deployments", k8sHandler.ListDeployments)