feat(source): support NodePort and ClusterIP service targets

Summary

EndpointTargetsFromServices currently considers only Service.Spec.ExternalIPs and Service.Status.LoadBalancer.Ingress when deriving DNS targets.

Requested behavior

Add support for service targets based on:

• Service.Spec.Ports with NodePort
• Service.Spec.ClusterIPs with ClusterIP

Acceptance criteria

• Define the target-selection behavior for NodePort and ClusterIP services.
• Add focused unit tests covering the supported service types and precedence with existing external IP and load balancer targets.
• Preserve current behavior for services that already expose external IPs or load balancer ingress addresses.

Relevant code: source/endpoints.go, EndpointTargetsFromServices.