Enhance AKS deployment preview with effective namespaces

[vhvb1989]

Follow-up from #10204.

Enhance the AKS deployment preview so it accurately describes the effective namespaces used by each deployment mechanism.

AKS service configuration supports a service-level namespace that acts as the default:

services:
  api:
    host: aks
    k8s:
      namespace: apps
      helm:
        releases:
          - name: redis
            namespace: data
          - name: ingress
            namespace: networking

During deployment:

• Kubernetes manifests and Kustomize generally use the service-level namespace.
• Helm releases without a namespace also use the service-level default.
• Individual Helm releases can override the namespace, such as data or networking above.

The initial preview reports only the service-level namespace, which can imply that every deployment mechanism uses it. This is acceptable for the initial delivery, but a more detailed preview should distinguish the default namespace from per-release Helm overrides.

Acceptance criteria

• Describe the service-level AKS namespace as the default namespace.
• Report the effective namespace for each configured Helm release.
• Preserve concise human-readable output while including detailed namespace information in structured output.
• Keep preview read-only and avoid Kubernetes cluster operations.
• Add coverage for Helm releases with inherited and explicitly overridden namespaces.

Source comment: #10204 (comment)