feat: schedule nightly off-host backups

deploy/systemd/dragons-stash-backup.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=Dragon's Stash off-host backup
+After=network-online.target docker.service
+Requires=docker.service
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+User=root
+EnvironmentFile=-/etc/dragons-stash/backup.env
+WorkingDirectory=/opt/stacks/DragonsStash
+ExecStart=/opt/stacks/DragonsStash/scripts/backup/run-backup.sh
+TimeoutStartSec=infinity

deploy/systemd/dragons-stash-backup.timer

@@ -0,0 +1,11 @@
+[Unit]
+Description=Nightly Dragon's Stash off-host backup
+
+[Timer]
+OnCalendar=*-*-* 03:00:00
+Persistent=true
+RandomizedDelaySec=15m
+Unit=dragons-stash-backup.service
+
+[Install]
+WantedBy=timers.target