Merged reverse-chronological activity feed for the Home page.

Blends recent items across the product into a single stream (newest first, capped at 30). Each item has the shape::

{"kind", "title", "subtitle", "status", "ts", "url"}

kind is one of audit | test_flow | draft | report | activity. ts is an ISO-8601 string. Sources with no rows simply contribute nothing — the endpoint is best-effort and fail-silent per source so one broken query can't blank the feed.