FL-1110 fix: keep external_client_id and reservation id out of RawPayload
redact() now also clears client_id and the vendor reservation id: both dereference to guest PII via our POS API key (D-48 logic), so they must never sit in the stored audit RawPayload. The typed DTO still carries the reservation id transiently. Tests assert both are cleared and absent from RawPayload.
Closes FL-1110