feat: 完善告警规则配置页面 — 增删改查弹窗 + 修复白屏bug + UpdateRule notify_channels序列化修复

- AlertManager: 新建/编辑告警规则弹窗(规则名称/描述/类型/数据源/表达式/级别/持续时间/通知渠道Switch)
- AlertManager: 修复白屏bug — getRules返回{list,total}未解包导致rules.map崩溃(Frontend Pitfall #1)
- AlertManager: 修复规则列表字段显示 — 原引用不存在的rule.metric/operator/threshold字段,改为rule.source/expression
- AlertManager: 新增规则删除按钮(带确认)
- alert.go: 修复UpdateRule notify_channels序列化bug — 原直接赋值[]string到text列导致500,改用toJSON()
- 同步提交前序未提交改动(WebShell/K8s/Server/Login等组件改进)

backend/internal/api/handlers/k8s.go

@@ -102,7 +102,10 @@ func (h *K8sHandler) CreateCluster(c *gin.Context) {
 		Name:        req.Name,
 		Code:        req.Code,
 		Version:     req.Version,
-		APIEndpoint: req.APIEndpoint,
+		ConfigType:  req.ConfigType,
+		APIServer:   req.APIServer,
+		APIEndpoint: req.APIServer, // auto-sync
+		Token:       req.Token,
 		KubeConfig:  req.KubeConfig,
 		Description: req.Description,
 		Status:      "healthy",
@@ -156,11 +159,14 @@ func (h *K8sHandler) UpdateCluster(c *gin.Context) {
 	}
 
 	updates := map[string]interface{}{
-		"name":         req.Name,
-		"version":      req.Version,
-		"api_endpoint": req.APIEndpoint,
-		"kube_config":  req.KubeConfig,
-		"description":  req.Description,
+		"name":        req.Name,
+		"version":     req.Version,
+		"config_type": req.ConfigType,
+		"api_server":  req.APIServer,
+		"api_endpoint": req.APIServer,
+		"token":       req.Token,
+		"kube_config": req.KubeConfig,
+		"description": req.Description,
 	}
 
 	if err := h.db.Model(&cluster).Updates(updates).Error; err != nil {