The TRUNCATE of impersonation_sessions/audit_logs was running after the
staff upsert. When a prior seed left impersonation_sessions rows
referencing staff records, ON CONFLICT DO UPDATE on staff violated the
FK constraint on impersonation_sessions.staff_id.
Moving the TRUNCATE before the staff block ensures all impersonation rows
are cleared before any staff insert/update attempt.
Co-Authored-By: Paperclip <noreply@paperclip.ing>