feat: add login authentication and certificate expiry notifications

- JWT-based login with ADMIN_USER/ADMIN_PASSWORD env config
- Login page with auth guard for Vue frontend
- Feishu bot webhook notification for expiring certificates
- SMTP email notification for expiring certificates
- Daily 8:00 AM cron for expiry checks
- Startup health check notification

autossl.service

@@ -10,6 +10,18 @@ WorkingDirectory={{DEPLOY_DIR}}/backend
 Environment="PORT=9090"
 Environment="ACME_PORT=8082"
 Environment="GIN_MODE=release"
+Environment="ADMIN_USER=admin"
+Environment="ADMIN_PASSWORD=您的密码"
+Environment="JWT_SECRET=请修改为随机字符串"
+# 飞书通知（可选）
+# Environment="FEISHU_WEBHOOK_URL=https://open.feishu.cn/open-apis/bot/v2/hook/xxx"
+# 邮件通知（可选）
+# Environment="SMTP_HOST=smtp.example.com"
+# Environment="SMTP_PORT=587"
+# Environment="SMTP_USER=user@example.com"
+# Environment="SMTP_PASSWORD=password"
+# Environment="SMTP_FROM=autossl@example.com"
+# Environment="NOTIFY_TO=admin@example.com"
 ExecStart={{DEPLOY_DIR}}/backend/autossl
 Restart=always
 RestartSec=3