New /imaging/delete_all endpoint wipes every per-bay JSON in IMAGING_DIR
via imaging_status.delete_all_sessions(). Template adds "Clear all"
outline-danger button next to the count badge, gated on sessions list
non-empty, with confirm() prompt naming the count.
Deployed via scp + systemctl restart pxe-webapp on 172.16.9.1.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>