Start an async XLSX export of the current company's orders, one row per order line. scope: 'all' exports every active order, 'filtered' applies the same filters and search as GET /orders, 'selected' exports the given orderIds. sort is honoured in all scopes so the file matches the on-screen order. Returns an exportId — poll GET /exports/:id for status; an email and in-app notification carry the download link when the file is ready.