After AI extraction, check if the roaster and roast already exist by
slug. When matched, show compact summary cards instead of full edit
forms. Each card has a "Change" link to revert to the form if the
match is wrong.
- Add match_existing_entities() for slug-based roaster/roast lookup
- Return _matched-roaster-id and _matched-roast-id signals from extraction
- Add submit_existing_roast() path to skip creation when roast exists
- Dynamic submit buttons: Save Roaster & Roast / Save Roast / Open Bag
- Hidden inputs bound to signals handle all form submission cleanly
202dafb9b9