Dockerfile builds apps/backoffice into /srv/admin and the old admin with
base /old/; nginx serves /old/ with its own uncached index.html.
Worker notification links point to the new admin pages (moves, requests,
chats); BACKOFFICE_URL defaults to ADMIN_URL.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>