fix(prometheus): exclude xui services from TraefikServiceHighLatency

Long-lived VPN WebSocket sessions inflate P95 request duration; keep 5xx/down/cert alerts for xui unchanged.

prometheus-stack/k8s/traefik-alerts.yaml

@@ -42,7 +42,7 @@ spec:
         - alert: TraefikServiceHighLatency
           expr: |
             histogram_quantile(0.95,
-              sum(rate(traefik_service_request_duration_seconds_bucket[5m])) by (le, service)) > 2
+              sum(rate(traefik_service_request_duration_seconds_bucket{service!~"xui-xui-service-.*"}[5m])) by (le, service)) > 2
           for: 5m
           labels:
             severity: warning