[feature] Charts CRD: support `platform` key for images resolved via `add-image`

[ikunduraci]

Is this Feature/Enhancement related to an Existing Problem? If so, please describe:

• The Images CRD supports a per-image platform key, but the Charts CRD does not. Images resolved via add-images: true are always synced as the full multi-arch index — e.g. kube-vip/kube-vip:v1.0.4 pulls ~10 child manifests (amd64, arm64, armv7, ppc64le, ...)

Describe Proposed Solution(s):

• Support a platform key on Charts entries, applied to images resolved via add-images: true:

  charts:
    - name: kube-vip
      repoURL: https://kube-vip.github.io/helm-charts/
      version: 0.9.9
      add-images: true
      platform: linux/amd64

Describe Possible Alternatives:

• hauler store sync --platform linux/amd64 works, but is global to the whole sync rather than per-entry, and isn't easily discoverable from the Charts CRD docs.
• Re-declaring each chart image in an Images block with platform: set — defeats the purpose of add-images.
• At minimum: document that the Charts CRD does not support platform and that --platform on hauler store sync is the way to constrain chart-resolved images.

Additional Context:

• Hauler version: 1.4.3
• OS/Arch: linux/amd64 (Alpine container, GitLab CI)
• Destination registry: self-managed GitLab container registry