Bulk-cancels every job in queued state for this printer, including jobs that are waiting while the printer is paused; none of them is sent to the printer. Jobs in printing state are intentionally not cancelled — a mid-print abort is unsafe over TCP/9100 because the raster data is already on the wire; a page job the IPP printer already holds is left to finish as well (cancel it with POST /api/v1/jobs/{id}/cancel). An API key without admin scope cancels only the queued jobs it submitted; the jobs of other keys and of browser or SSO users stay queued. Returns 204 even when there are no queued jobs.