Grafana agent autodiscovery requires app=weaviate label

Grafana agent's Kubernetes service discovery for Weaviate pods depends on the app=weaviate label being present on pods.

Configure Grafana agent scrape config with kubernetes_sd_configs using role: pod and selector label: app=weaviate. This label is automatically added by the Weaviate helm chart. Verify the label exists on pods if autodiscovery fails: kubectl get pods -l app=weaviate