Add Checkbox ETTN receipts for Nova Poshta COD waybills

Cashier creates an ETTN receipt in Checkbox bound to the TTN with payment
control; Checkbox fiscalizes it itself when the parcel is paid for.

- cash_registers (Fernet-encrypted license key / PIN) and receipts tables
- Checkbox HTTP client + stub (ETTN does not work on test registers)
- two-phase create via ARQ job, timeout reconciliation, cron status polling
- /receipts and /cash-registers API, audit records
- dashboard: per-order and bulk create, prepayment, cancel; cash registers page

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/app/api/v1/orders.py

@@ -9,6 +9,7 @@ from app.db.models.audit import AuditAction
 from app.schemas.orders import OrderRowOut
 from app.services import audit
 from app.services import orders as orders_service
+from app.services import receipts as receipts_service
 
 router = APIRouter(prefix="/orders", tags=["orders"], dependencies=[Depends(require_any)])
 
@@ -21,7 +22,10 @@ async def list_orders(
     # CRM-алиасы (SKU/Name/...) вместо snake_case полей, которые ждёт фронтенд.
     await orders_service.sync_orders_from_crm(session, crm)
     orders = await orders_service.list_orders(session, has_receipt=has_receipt)
-    return [OrderRowOut.from_order(order) for order in orders]
+    receipts = await receipts_service.latest_receipts_by_order(
+        session, [order.id for order in orders]
+    )
+    return [OrderRowOut.from_order(order, receipts.get(order.id)) for order in orders]
 
 
 @router.delete("/{order_id}", status_code=status.HTTP_204_NO_CONTENT)