feat: register Network Services in the service catalog (Phase 1)

[kevwilliams]

Implements Phase 1 of the service-catalog-registration design brief (PR #156, issue #155): pure YAML, no Go changes.

What this PR adds

A Kustomize bundle under config/services/ that registers Network Services in the platform service catalog and declares its monitored resource and meters:

• Service (services.miloapis.com/v1alpha1)
  • serviceName: networking.datumapis.com
  • phase: Draft
  • owner.producerProjectRef.name: datum-cloud
• ServiceConfiguration (services.miloapis.com/v1alpha1)
  • Monitored resource: HTTPRoute (gateway.networking.k8s.io)
  • Six optional dimensions: region, gateway, gateway_namespace, gateway_class, httproute_name, httproute_namespace
  • Four meters inline under networking.datumapis.com/gateway/*: requests, egress-bytes, ingress-bytes, connection-seconds

Bundle layout

config/services/
  kustomization.yaml
  networking.datumapis.com/
    kustomization.yaml      # kind: Component
    service.yaml
    serviceconfiguration.yaml

Matches the per-service-domain layout used by compute in datum-cloud/datum. The inner kustomization.yaml is a Kustomize Component, mirroring the compute reference.

What this PR does NOT add

• No MonitoredResourceType or MeterDefinition resources directly — those are produced by the catalog's fan-out controller from ServiceConfiguration.spec, so no config/billing/ bundle is needed.
• No Go code changes — Phase 1 is YAML-only.
• No Flux wiring — that is a separate step in datum-cloud/infra handled by the platform/infra team after sign-off.

Phase 2 (usage emission from the edge proxy) remains blocked on OD-5 through OD-8 in the design brief.

Test plan

• kubectl kustomize config/services/ renders both resources without error
• Reviewer confirms Service and ServiceConfiguration shapes match the catalog CRDs in the deployment target
• After merge: platform/infra wires config/services/ into Flux; confirm the fan-out controller produces the expected MonitoredResourceType and MeterDefinition resources in the billing namespace
• Confirm Service appears in the catalog in Draft phase

Refs #155. Design brief: PR #156.