Standalone `docker exec trivy-service trivy image ...` opens the vuln-DB cache
the long-lived server already holds, failing with "cache may be in use by
another process: timeout" — so every scan silently returned [] (apps: 0 even on
vulnerable images). Point the exec'd client at the server (--server
http://localhost:4954, the container's fixed --listen port); the server owns the
DB, the client just submits the image. Verified against alpine:3.10.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>