feat(admin): order management

Sprint 23.

New features/admin/orders/ module, same container/facade/service split as
admin/products and admin/categories.

- AdminOrder model + AdminOrdersLocalGateway seeding 24 deterministic
  synthetic orders (no real order data source exists anywhere in this
  repo - explicitly a placeholder, not a mock of production volume)
- list: search, status filter, pagination, CSV export (client-side Blob
  download)
- detail: customer/payment/shipping, itemized total, status timeline,
  change-status dropdown, refund request + cancel (window.confirm-gated),
  separate customer-facing vs internal notes, print invoice via
  window.print() with @media print hiding non-invoice chrome
- wired into /:lang/backoffice/orders(/:id), replacing the coming-soon
  placeholder

docs/ADMIN.md + docs/BACKEND.md updated; dashboard's Orders/Revenue cards
(Sprint 19) remain intentionally un-wired to this mock and still render
pending-backend.

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

docs/ADMIN.md

@@ -291,6 +291,29 @@ implementation) + `features/backoffice/media/` + the shared
   API and rebinding the provider; no consumer (`MediaLibraryFacade`,
   `MediaPickerComponent`, or any of the pickers above) changes.
 
+## Sprint 23 - Orders (mock/local)
+
+`features/admin/orders/` (model/gateway/facade/pages), same
+container/facade/service split as the rest of `admin/*`:
+
+- **No real data source exists for orders anywhere in this repo** (already
+  called out in Sprint 19's dashboard gap and `docs/BACKEND.md` item 7) -
+  `AdminOrdersLocalGateway` seeds 24 deterministic synthetic orders in
+  memory (cycling through all statuses/customers) rather than reading from
+  `BackofficeDataService`, since there is nothing there to read. This is
+  explicitly a placeholder to unblock the admin UI, not a real mock of
+  production order volume.
+- List: search (order number/customer/email), status filter, pagination,
+  CSV export (client-side `Blob` download, no server round-trip).
+- Detail: customer/payment/shipping info, itemized line items + total,
+  status timeline, change-status dropdown, refund request and cancel
+  (both `window.confirm`-gated), customer-visible notes vs internal-only
+  notes (two separate free-text logs), print invoice via `window.print()`
+  with a `@media print` rule hiding all non-invoice chrome (`.no-print`) -
+  no PDF generation library, deliberately minimal.
+- Wired into `/​:lang/backoffice/orders` and `/​:lang/backoffice/orders/:id`,
+  replacing the coming-soon placeholder.
+
 ## Known gaps / backend needs
 
 - **Dashboard metrics endpoint.** Categories/Products counts are computed