Rows without a cover (cover_url NULL or N/A) show a + button.
Clicking it opens a modal to enter a URL which is saved via new
PATCH /api/records/{id}/cover_url endpoint. cover_image is cleared
so n8n picks it up on the next backfill run.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>