fix(webui): slow metrics chart refresh to 3s interval

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/api.go

@@ -592,7 +592,7 @@ func (h *handler) handleAPIMetricsStream(w http.ResponseWriter, r *http.Request)
 	if !sseStart(w) {
 		return
 	}
-	ticker := time.NewTicker(time.Second)
+	ticker := time.NewTicker(3 * time.Second)
 	defer ticker.Stop()
 	for {
 		select {