Backfill Legacy Submitted Document Requests

Move every pre-review-workflow request reading SUBMITTED to FULFILLED, so nobody inherits a review backlog of their entire history.

Status only: no FULFILLED document_request_events row is written. The absence of an event log is exactly what identifies these rows, and fabricating a sign-off would attribute a review to a company and a moment that never happened. Consumers already tolerate this — _review_details (backend/api/document_requests.py) reports the reviewer as absent for a FULFILLED row with no event.