Manufacturing boards

A configurable execution board ("tablero de comandas"), the same idea as `app_s.restaurant.Command` (the kitchen display board for sales orders) but for `ManufacturingOrder`: a public URL, filtered by branch and optionally by the produced element's category, listing PLANNED orders with a one-click "Ejecutar" button - the feature the owner asked for after seeing StarOffice's and Ultrapez's own hand-rolled "Comanda digital" pages (README_LINEA_DE_PRODUCCION.md section on tenant_9267/tenant_8077): several boards can exist per company (e.g. one per kitchen station or workshop area), each showing only what it is configured to show. Unlike Command's public view (deliberately anonymous, for an unattended kitchen tablet), this board requires a logged-in staff user: executing an order books real inventory and accounting movements, StarOffice/Ultrapez's pages did that too but through a raw, unaudited API call - this board goes through the same `execute_order()` service the admin action uses, with the same validations.