- Remove unused `completed_jobs` list (dead code after per-job update refactor)
- Wrap DB update in try/except to prevent one failed update from aborting remaining jobs
- Add test assertions verifying batch_processed, status, and file_object are written to DB
CheckBatchCost poller updated the status column but not the file_object
JSON column. The list_batches endpoint reads status from file_object,
so batches appeared stuck in "validating" even after Azure reported
them as completed. Now update file_object alongside status in the
per-job DB write.
Ryan Crabbe