feat(deploy): add an example systemd service

Provide a dedicated-user service with automatic restart and restricted file permissions.

deploy/reximemo-ose.service

@@ -0,0 +1,21 @@
+[Unit]
+Description=RexiMemo Open Source Edition
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=reximemo-ose
+Group=reximemo-ose
+WorkingDirectory=/opt/reximemo-ose
+ExecStart=/opt/reximemo-ose/.venv/bin/python -u /opt/reximemo-ose/server.py
+Restart=on-failure
+RestartSec=5
+Environment=PYTHONUNBUFFERED=1
+Environment=PYTHONDONTWRITEBYTECODE=1
+NoNewPrivileges=true
+PrivateTmp=true
+UMask=0027
+
+[Install]
+WantedBy=multi-user.target