test(e2e): cover the computeplane module end-to-end #3369

Follow-up from the #3280 review (not blocking the merge): the computeplane module ships with helm-unittest suites pinning the module contract (release name / kubeconfig Secret, inline addon pins, nodeGroups validation), but no e2e coverage.

An e2e scenario should, on a real cluster: enable computeplane: true on a tenant, wait for the wrapped kind: Kubernetes cluster to provision (Kamaji control plane + KubeVirt workers), assert the computeplane-admin-kubeconfig Secret exists and is not tenant-visible, assert the pinned addons (fluxcd, cert-manager, ingress-nginx Proxied) come up inside the cluster, and tear the module down cleanly (remote HelmReleases deleted before the cluster is deprovisioned).

Standing up a full Kamaji + KubeVirt cluster in CI is a real cost, which is why this is a follow-up rather than a merge condition for #3280. It should land together with (or right after) the placement: ComputePlane routing work in cozystack-api, which the same scenario would exercise end-to-end with a real catalog app.

Ref: design — https://github.com/cozystack/community/tree/main/design-proposals/compute-plane; implementation — #3280.