POST /invoices

curl -X POST https://api.kestrelledger.eu/v1/invoices \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"customer_id": "cus_7", "items": [{"name": "Разработка", "qty": 10, "price": 60}], "currency": "EUR"}'

{
  "id": "inv_204",
  "number": "2026-0204",
  "status": "draft"
}