Non-interactive equivalent of system-admin-toj's prune-docker.sh, which
prompts per stage and so cannot run from cron.
Only the stages that discard regenerable data run by default: build
cache and dangling images. Unused images and volumes are opt-in, because
docker volume prune removes volumes belonging to merely-stopped
containers rather than only orphaned ones, which on this host is a
plausible way to lose a database.
A failing stage is reported and the remaining stages still run, since a
partial reclaim beats none, but the task still ends up failed so the
error is not swallowed.
Co-Authored-By: Claude <noreply@anthropic.com>
