Read https://veyqo.org/llms.txt and https://veyqo.org/openapi.json. Inspect this application's stack and stored order model. Integrate server-created Veyqo hosted checkout, a durable signed webhook handler and idempotent order fulfilment. Keep prices and keys server-side. Save session/payment IDs and persisted operation keys. Explain how retries, refund status, checkout attempts, shared provider accounts and each relevant error are handled. Use exact documented fields and verify returned status/amount/currency/ownership before fulfilment. Add meaningful tests and list required dashboard settings and environment variables. Do not deploy.