Add production Jenkins release pipelines

deploy/systemd/spacetimedb.service

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+[Unit]
+Description=SpacetimeDB Server
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=spacetimedb
+Group=spacetimedb
+WorkingDirectory=/stdb
+ExecStart=/stdb/spacetime --root-dir=/stdb start --listen-addr=127.0.0.1:3000
+Restart=always
+RestartSec=5
+LimitNOFILE=1048576
+
+# 生产库只监听本机端口，由 Nginx 暴露最小客户端路由。
+NoNewPrivileges=true
+PrivateTmp=true
+ProtectSystem=full
+ReadWritePaths=/stdb
+
+[Install]
+WantedBy=multi-user.target