Add the dinners API for Regulars

POST /api/v1/dinners adds a Regular from a name or a recipe link
(status and origin regular, grounding_status pending), refusing a name
harness.Similar to an unarchived dinner, or a known link, with 409.
GET /dinners?status=regular|quest_log lists dinners with photo URLs and
grounding status; PATCH /dinners/{id} edits name, method, minutes and
difficulty; DELETE archives the row; POST /dinners/{id}/favorite toggles
is_favorite. Every write records the session subject as updated_by.

Migration 0008 adds dinners.recipe_url so a pasted link is kept until
grounding resolves it.

Maestro task 28d3cb4b-83d1-40e8-991f-d88f0f64d270.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/server/settings.go

@@ -110,7 +110,7 @@ func decodePatch[T any](body io.Reader) (T, error) {
 		if errors.As(err, &typeErr) {
 			return patch, fmt.Errorf("%s: want a JSON %s", typeErr.Field, typeErr.Type)
 		}
-		return patch, fmt.Errorf("invalid settings: %v", err)
+		return patch, fmt.Errorf("invalid request body: %v", err)
 	}
 	return patch, nil
 }