Metrics are served on METRICS_PORT (default 2112, "off" to disable), never on the public port. Besides the Go runtime and process metrics this adds: - http_requests_total and http_request_duration_seconds per route pattern, from an Echo middleware. - musicserver_songs_requested_total and musicserver_songs_played_total by pick mode (random, low, classic). The mode is now stored with each queued song (migration 000006, not released yet). - Library size, sync duration, last successful sync, broken songs from the last full sync, and the database connection pool. Refs #35, #36, #37 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>