[APIView] One-time cleanup: remove stale pending automatic revisions accumulated by cleanup bug

Two bugs in `CreateAutomaticRevisionAsync`

1. The cleanup loop exited early on a content-hash match, leaving older pending revisions behind.
2. When a stale candidate didn't match incoming content, it was not deleted before the new revision was created.

As a result, production reviews may have accumulated multiple stale pending automatic revisions that should have been deleted.

### Task

Write a one-time migration/backfill job that applies the same cleanup invariant retroactively to all existing reviews:

- For each review, fetch all automatic revisions ordered newest → oldest
- Walk the list and keep only the newest unprotected pending revision since the last approval/released/commented anchor
- Soft-delete all older unprotected pending revisions between the newest pending and the anchor
- Respect version scoping — only clean up revisions belonging to the same `APIVersionId`
- Respect hard-stop boundaries — do not touch any revision that is approved, released, or has comments

### Acceptance Criteria

- [ ] All reviews have at most one pending automatic revision per version since the last approval anchor
- [ ] No approved, released, or commented revisions are touched
- [ ] The job is idempotent — safe to run multiple times
- [ ] The job logs how many revisions were deleted per review for auditability