Adds the two columns the background-removal feature (#281) is built on: item_drafts.remove_background (boolean, not null, default true) records the submitter's per-submission intent, and item_images.original_image_path (nullable text, no default) records where a cut-out photo came from so it can be restored. The default on remove_background is load-bearing — any row written by a path that does not mention the column behaves like the new default, so no backfill is needed. original_image_path stays null until a photo has actually been cut out, which doubles as the answer to "can this be restored?" rather than needing a separate flag. Also updates the Drizzle mirror in src/db-drizzle/schema.ts by hand (the local dev database was not running to re-pull from) and adds the integration test backgroundRemoval.integration.test.ts, including the exported seedSubmission helper that Task 3 will reuse.
Closes#281
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
