Issue a public credit link or personal email invitations [admin]

Only allowlisted administrators can use these operations. Use one UUID requestId per campaign and reuse the identical body after timeouts. Personal emails are deduplicated and each gets a distinct, email-bound single-use code. Existing verified, unbanned recipients are credited immediately. sendEmail explicitly authorizes product email. Code creation is atomic; delivery/credit failures are per recipient. Retry the same request for retry_needed credit results; never change requestId just to retry. Email status sent means SES accepted, not inbox delivery. Sending/uncertain attempts are not automatically resent; use the returned personal link for manual delivery. Responses contain bearer codes: keep private. A different body with the same requestId returns 409.