Flushes world via rcon (save-off + save-all flush) before tarring
when the server is running; skips the flush and archives as-is when
the container is down. Outputs timestamped archives to backups/,
which is gitignored.
Tracks docker-compose config, server scripts, and server properties.
Runtime data (world, libraries, versions, logs, jar), credentials, and
backup snapshots are gitignored.
