feat(updates): check Gitea automatically and deploy on owner confirmation

Add owner-only update controls, a read-only SSH checker and independent systemd deployment services. Build before maintenance; back up code and database; restore on failed deployment. Preserve runtime configuration and gate business writes during the switch.

deploy/server/systemd/replypier-update-recover.service

@@ -0,0 +1,15 @@
+[Unit]
+Description=Recover an interrupted ReplyPier deployment before accepting traffic
+After=docker.service
+Requires=docker.service
+Before=replypier-backend.service replypier-knowledge.service
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/python3 /opt/replypier-updater/cli.py recover-boot
+RemainAfterExit=yes
+TimeoutStartSec=20min
+UMask=0077
+
+[Install]
+WantedBy=multi-user.target