Import members and data

Queues up to 25,000 Signals (or a public CSV / Google Sheet URL) as one operation and answers at once with operationId and pollUrl. Each line is identified like an add (saved data unless live: true); with families, the data you ask for (profile, company, contact_email, contact_phone) is then fetched for each member, new or already on the List. Data a member already holds is not bought again. Above 25 credits of worst-case estimate, a request with families needs maxCredits, the most it may spend: the operation stops at that ceiling (stopReason max_credits) and can be resumed with a higher one. With webhookUrl (public HTTPS), that URL receives one POST each time the operation stops moving (completed, stopped, cancelled); the event carries no member data, read the operation at its pollUrl. Lines naming the same identity with the same externalId are deduplicated. Replaying with the same operationId returns the same operation and never charges twice. To stop it, cancel it (operations/{operationId}/cancel): cancelling is final, a new run needs a new operationId.