新增自动化部署：Gitea Actions + systemd + gunicorn

- .gitea/workflows/deploy.yml：push main 自动触发部署
- requirements.txt：Python 依赖清单
- deploy/opc-manager.service：systemd 服务（gunicorn --preload -w 4）
- deploy/README.md：完整部署指南
- deploy/服务器配置任务提示词.md：给服务器管理 Agent 的操作提示词
- health 接口简化返回 {ok, service}

deploy/opc-manager.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=OPC Manager (Flask)
+After=network.target mysql.service
+
+[Service]
+Type=simple
+WorkingDirectory=/opt/opc-manager/current
+ExecStart=/opt/opc-manager/current/.venv/bin/gunicorn --preload -w 4 -b 0.0.0.0:5177 backend.flask_app:app
+Restart=on-failure
+RestartSec=5
+EnvironmentFile=/opt/opc-manager/current/.env
+
+[Install]
+WantedBy=multi-user.target