fix: repair Rentman equipment sync with real API field mapping

- Map real Rentman fields: price -> rental_price, folder -> category/subcategory
  (resolved via folder hierarchy to top-level categories), code -> number,
  shop_description_long (fallback short/external_remark) -> description (HTML stripped)
- Sync only in_shop items; exclude archived/temporary from public catalog
- Extract known brands from equipment names (d&b, Shure, Pioneer, ...)
- Build specifications from physical fields (power, weight, dimensions)
- Persist equipment images in docker volume (survive redeploys)
- Router: filter available items, add price_asc/price_desc sorting
- Frontend: show prices in catalog card, detail page and cart with
  per-day subtotal; price sorting options
- Tests: use real Rentman field names in fixtures, mock folder_map

docker-compose.yml

@@ -41,6 +41,7 @@ services:
     - MCP_AUTH_TOKEN=${MCP_AUTH_TOKEN:-}
     volumes:
     - /var/run/docker.sock:/var/run/docker.sock
+    - equipment_images:/data/images
     restart: unless-stopped
     healthcheck:
       test:
@@ -98,3 +99,4 @@ networks:
 volumes:
   postgres_data: null
   redis_data: null
+  equipment_images: null