The MQTT completion handler stored "aborted" as the queue item status
when a print was cancelled mid-print, but the response schema only
allows "cancelled". Pydantic validation failed on the invalid status
when listing all queue items, returning 500. Filtering by specific
status excluded the bad row so those still worked.
Normalise "aborted" → "cancelled" before storing. A startup fixup
also converts any existing "aborted" rows in the database.