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/cron-backup.conf

@@ -0,0 +1,54 @@
+# Cron 备份配置示例
+# 使用方法: crontab -e 并添加以下行
+
+# 环境变量设置
+SHELL=/bin/bash
+PATH=/usr/local/bin:/usr/bin:/bin
+BACKUP_DIR=/opt/user-management/backups
+DB_PATH=/opt/user-management/data/user_management.db
+CONFIG_PATH=/opt/user-management/configs/config.yaml
+RETENTION_DAYS=30
+
+# ============================================
+# 备份任务
+# ============================================
+
+# 每天凌晨 2:00 执行备份
+0 2 * * * /opt/user-management/scripts/backup/backup.sh >> /var/log/backup.log 2>&1
+
+# 每周日凌晨 3:00 执行完整备份（包含上传到远程存储）
+0 3 * * 0 /opt/user-management/scripts/backup/backup.sh && \
+  scp /opt/user-management/backups/latest.tar.gz backup@remote-server:/backups/
+
+# 每天下午 6:00 检查备份状态并发送报告
+0 18 * * * /opt/user-management/scripts/backup/backup.sh --verify || \
+  echo "Backup verification failed" | mail -s "Backup Alert" admin@example.com
+
+# ============================================
+# 清理任务
+# ============================================
+
+# 每月 1 日凌晨 4:00 清理超过 90 天的备份
+0 4 1 * * find /opt/user-management/backups -name "*.tar.gz" -mtime +90 -delete
+
+# ============================================
+# 监控任务
+# ============================================
+
+# 每 15 分钟检查服务健康状态
+*/15 * * * * curl -sf http://localhost:8080/api/v1/health || \
+  echo "Service down at $(date)" | mail -s "Service Alert" admin@example.com
+
+# ============================================
+# 日志轮转配置 (/etc/logrotate.d/user-management)
+# ============================================
+
+/var/log/backup.log {
+    daily
+    rotate 7
+    compress
+    delaycompress
+    missingok
+    notifempty
+    create 644 root root
+}