fix(docker): start crond and persist acme.sh state so cert renewal works
The image shipped busybox crond but the entrypoint never started it, and the acme.sh crontab entry vanished on every container recreation, so certificates issued via the panel's SSL menu silently expired after 90 days. The entrypoint now re-registers the acme.sh cron job and starts crond when acme.sh is installed, and docker-compose gains an acme volume so renewal state survives recreation.
Closes #5116