Submit an async address-validation job (up to 50,000)

Queue a large address list for asynchronous validation — the path for lists larger than the 200-address synchronous /validate/batch cap. Returns a job_id immediately (HTTP 202); poll GET /validate/jobs/{job_id} for status and results, or pass webhook_url and the server POSTs {job_id, status, addresses_count} when processing finishes. Billing is per row inside the worker — each address consumes one address-validation transaction (Stripe-plan transaction; the trial pool decrements 1 regardless), so there is no submit-time 402/403. If the account runs out of transactions partway through, the remaining results carry an error entry rather than failing the whole job. Requires an API key. Runs on the main box only (the UK PAF satellite returns 503 with a redirect hint).