In POST /reviews/:diagnosisId, perform the conditional diagnoses update
first with .returning() to determine whether a row was updated. The update
WHERE includes both id and status 'needs_review'. If no row is returned,
return badRequest and do not insert an expert review. Only after a
successful update insert expertReviews. This prevents concurrent reviewers
from both inserting review rows when only one update should win.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
