Rename the old CHAR(36) id to uuid (still used for public URLs and file
naming) and add a real auto-increment id as the primary key. Track
input/output file size and conversion duration per job. Cleanup no
longer deletes rows; it marks cleaned_at and skips already-cleaned
expired jobs on later runs.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>