docs: add runbooks and Kubernetes Helm Chart

Add 6 runbook documents:
- 服务启动 (Service Startup)
- 服务停止 (Service Shutdown)
- 配置更新 (Configuration Update)
- 日志分析 (Log Analysis)
- 备份恢复 (Backup & Recovery)
- 安全事件 (Security Incident)

Add Kubernetes Helm Chart:
- Chart.yaml, values.yaml
- Deployment with health checks
- Ingress with TLS support
- PVC for data persistence
- PDB for high availability
- HPA for autoscaling
- ServiceAccount configuration

Add cron-backup.conf for automated backup scheduling.

kubernetes/user-management/templates/serviceaccount.yaml

@@ -0,0 +1,6 @@
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: {{ include "user-management.serviceAccountName" . }}
+  labels:
+    {{- include "user-management.labels" . | nindent 4 }}