add explicit app label for metrics selector

Service Monitor is configured to select on match label, but service template did not explicitly set app label in metadata.

Broken ex below


~ kdsvc my-rollup-metrics
Name:              my-rollup-metrics
Namespace:         my-ns
Labels:            
                   app.kubernetes.io/managed-by=Helm

~ kd servicemonitor
Name:         my-rollup-metrics
Namespace:    my-ns
Labels:       app=my-rollup-astria-dev-cluster
              app.kubernetes.io/managed-by=Helm
              release=kube-prometheus-stack
Annotations:  meta.helm.sh/release-name: my-rollup
              meta.helm.sh/release-namespace: my-ns
API Version:  monitoring.coreos.com/v1
Kind:         ServiceMonitor
Spec:
  Endpoints:
    Path:     /debug/metrics/prometheus
    Port:     geth-metrics
  Job Label:  geth-metrics
  Namespace Selector:
    Match Names:
      my-ns
  Selector:
    Match Labels:
      app:  my-rollup-astria-dev-cluster

astriaorg / dev-cluster

add explicit app label for metrics selector #177