Merged via /merge-batch (v3.8.51 provenance sweep). Boarded and validated together with the batch's other provenance PRs in a combined worktree — full gate suite green. Thank you.
Integrated into release/v3.8.8. Applied review fixes: moved the SELECT 1 into a pingDb() db helper (no raw SQL in route, Hard Rule #5) + the 503 catch no longer leaks err.message (Hard Rule #12). Thanks @herjarsa!