⭐️ publish helm charts to OCI

[chris-rock]

Summary

• Add OCI registry publishing for the Helm chart to GHCR alongside the existing GitHub Pages publication
• Users can now install the chart via oci://ghcr.io/mondoohq/mondoo-operator/charts/mondoo-operator

Closes #1359

Changes

• Added packages: write permission to the release-helm job
• Added GHCR login step using docker/login-action
• Added step to package and push the Helm chart to the OCI registry

Usage

OCI method (new)

helm install mondoo-operator oci://ghcr.io/mondoohq/mondoo-operator/charts/mondoo-operator --version <version>

GitHub Pages method (still works)

helm repo add mondoo https://mondoohq.github.io/mondoo-operator  
helm install mondoo-operator mondoo/mondoo-operator

Test plan

• Push a version tag and verify the chart appears at ghcr.io/mondoohq/mondoo-operator/charts/mondoo-operator
• Test pulling the chart: helm pull oci://ghcr.io/mondoohq/mondoo-operator/charts/mondoo-operator
• Verify existing GitHub Pages installation method still works

[github-actions]

Test Results

  5 files  ±0   41 suites  ±0   33m 24s ⏱️ - 6m 21s
282 tests ±0  282 ✅ ±0  0 💤 ±0  0 ❌ ±0 
301 runs  ±0  299 ✅ ±0  2 💤 ±0  0 ❌ ±0 

Results for commit 5981bfd. ± Comparison against base commit c4f4051.