FL-1110 feat: add cps.customer.deleted contract (forward-declaration)
- EventNameCustomerDeleted + topic cps.customer.deleted
- CustomerDeleted{ID} minimal payload (id only, no PII) for right-to-erasure cascade
- dormant: CPS does not yet emit this event; confirm payload before enabling
- tests: Validate(required id), GetEventName, PII-free guard