[ADD] website_sale_disable_cart: extract cart restriction from website_sale_aplicoop

The "shop as a read-only catalog" behaviour lived inside website_sale_aplicoop,
so every site that wanted the eskaera flow also lost the standard cart. It now
ships as its own installable addon, with the redirect target configurable
instead of hardcoded to /eskaera.

- website_sale_disable_cart: hides the cart UI (12 header styles + the product
  card quick-add) and overrides the standard cart endpoints. Redirect URL is
  configurable in Website settings (default /shop); only site-internal paths are
  accepted, so a misconfigured value cannot turn the shop into an open redirect
  nor loop back into a disabled route.
- Fixes carried over from the original code: /shop/cart/quantity is the Odoo 18
  path (it was /shop/cart_quantity, which never matched), the boxed, sidebar and
  sales two/three/four headers were not covered (the cart link stayed visible on
  them), and the routes now override the standard methods instead of registering
  duplicate ones.
- website_sale_aplicoop 18.0.1.12.0: drops the view file and the four redirect
  routes; installing it no longer touches the standard shop.

Upgrade order matters: update website_sale_aplicoop first, then install
website_sale_disable_cart in a second Odoo run — both use the same XPaths and
obsolete records are only cleaned up at the end of a run.

Tests: 8/8 in website_sale_disable_cart, aplicoop unaffected (its 2 failures
predate this change). Verified live on a DB clone: /shop/cart returns 303 to the
configured URL and no cart markup remains on /shop.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

website_sale_aplicoop/README_DEV.md

@@ -7,7 +7,8 @@ Sistema de pedidos colaborativos para grupos de consumo. Reemplaza el legacy Apl
 ## Resumen de funcionalidades
 
 - Gestión completa de órdenes de grupo (draft → confirmed → collected → invoiced → completed)
-- Carrito separado por grupo de consumo; tienda estándar de `website_sale` deshabilitada
+- Carrito separado por grupo de consumo (la tienda estándar de `website_sale` se
+  puede deshabilitar aparte con `website_sale_disable_cart`)
 - Control de catálogo por listas de inclusión (proveedores, categorías, productos) y exclusión (blacklists)
 - Cron diario de auto-confirmación + creación automática de lotes de picking
 - Paginación de productos (lazy loading) para cargas rápidas
@@ -86,7 +87,9 @@ Todos los endpoints viven bajo `/eskaera/`:
 | `POST /eskaera/<order_id>/confirm` | Confirmar carrito (sale.order en draft) |
 | `POST /eskaera/clear-cart` | Limpiar carrito actual |
 
-Las rutas `/cart` y `/shop` de `website_sale` están redirigidas a `/eskaera`.
+Las rutas estándar de `website_sale` (`/shop` y su carrito) no se tocan desde
+este módulo. Para desactivar el carrito estándar y redirigirlo a `/eskaera`,
+instala `website_sale_disable_cart` y configura la URL de redirección.
 
 **Seguridad portal:** los usuarios solo ven órdenes de su `consumer_group_id`. La regla `rule_group_order_company_read` incluye guardia `user.share`.