chore(deploy): disable watchtower image cleanup for rollback safety

After the v0.62.13 incident, we had no previous image to roll back to
because WATCHTOWER_CLEANUP=true deletes old images after each update.
Set to false so at least one prior image stays on disk as a rollback
target. Disk cost is negligible; rollback availability is not.

Applied live on both US and EU droplets alongside this template change.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: ToddHebebrand

deploy/eu/docker-compose.yml

@@ -226,7 +226,10 @@ services:
     restart: unless-stopped
     environment:
       WATCHTOWER_POLL_INTERVAL: 300
-      WATCHTOWER_CLEANUP: "true"
+      # Cleanup disabled so one previous image stays on disk for rollback.
+      # A weekly host cron prunes images older than 14 days to prevent
+      # unbounded growth: 0 3 * * 0 docker image prune -a --filter "until=336h" -f
+      WATCHTOWER_CLEANUP: "false"
       WATCHTOWER_LABEL_ENABLE: "true"
       DOCKER_API_VERSION: "1.54"
     volumes: