Improve movement flow layout/animation and fix Byzantine hall doors, styles, and preload.

Co-authored-by: Cursor <cursoragent@cursor.com>

Documentation/API.md

@@ -116,7 +116,7 @@ Only **admins** can create or promote **admin** accounts. Cannot deactivate/demo
 | Tour admin (`/api/tours/admin`, POST/PATCH/DELETE, stops) | `tours` | `tour.*` |
 | `/api/users/*` | `users` | `user.*` |
 
-**Public** (no login): all catalog `GET` routes, `POST /api/artists/:id/preload-images` (local file linking for 3D halls), `/images`, SPA static.
+**Public** (no login): all catalog `GET` routes, `POST /api/artists/:id/preload-images`, `POST /api/movements/:id/preload-images` (local file linking for 3D halls), `/images`, SPA static.
 
 Staff mutations are recorded in `curator_audit_log` with `user_id` (see [DB_structure.md](DB_structure.md)).
 
@@ -597,7 +597,7 @@ Both lists are grouped by art movement and exclude the current artist. Each arti
 
 **Public** — no curator login required.
 
-Fast local scan: links paintings to files already on disk. Does **not** download from the internet. The 3D client calls this automatically when entering an **artist** hall.
+Fast local scan: links paintings to files already on disk and regenerates missing thumbs. Does **not** download from the internet. The 3D client calls this automatically when entering an **artist** hall.
 
 **Response**
 
@@ -609,6 +609,20 @@ Fast local scan: links paintings to files already on disk. Does **not** download
 
 ---
 
+## `POST /api/movements/:id/preload-images`
+
+**Public** — no curator login required.
+
+Same local-only scan as the artist preload, for every painting by artists in the movement. The 3D client calls this automatically when entering a **movement** hall.
+
+**Response**
+
+```json
+{ "fetched": 40, "total": 45 }
+```
+
+---
+
 ## `GET /api/paintings/:id`
 
 Painting detail with influence graph neighbours.
@@ -921,6 +935,7 @@ The React client wraps these endpoints in `client/src/api/client.ts`. All reques
 | `api.getArtistNavigation(id)` | `GET /api/artists/:id/navigation` |
 | `api.getPainting(id)` | `GET /api/paintings/:id` |
 | `preloadArtistImages(id)` | `POST /api/artists/:id/preload-images` |
+| `preloadMovementImages(id)` | `POST /api/movements/:id/preload-images` |
 | `imageUrl(path, revision?)` | `/images/<path>` or placeholder; optional `?v=` cache buster |
 | `paintingImageRevision(painting, sessionRevision?)` | Prefer API `image_cache_key` / `thumbnail_cache_key`, else in-session counter |
 | `galleryImageUrl(painting, sessionRevision?)` | Local thumb/full only (3D); auto `?v=` from cache keys |