a gallery is a carousel

It always rendered as one — data-carousel, a snap track, two arrows, driven by
carousel.client.js. The entity was the last thing still calling it something
else, and that collided with the site's own Gallery section: two nav rows
reading Gallery and Galleries, meaning a list of objects and a list of
photograph sets.

GalleriesPanel, GalleryPicker and GalleryItems become Carousels*, the endpoint
becomes /fofos-admin/carousels, the block kind becomes carousel and
subject-gallery becomes subject-carousel. The publish allowlist follows the
renamed tables.

What did NOT move: GALLERY_CONFIG at /fofos-admin/gallery, subjects.ts's
base '/gallery', and home_gallery_media. Those are the Gallery section and the
legacy rows, and both are correct.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/sections/subjects.ts

@@ -26,7 +26,7 @@ import { Boxes, Shapes } from 'lucide-react';
 export type SubjectRecord = {
   id: number;
   /** The gallery holding its media, or null while nobody has chosen one. */
-  gallery_id: number | null;
+  carousel_id: number | null;
   title: string;
   slug: string | null;
   description: string | null;