Ensure packer-plugin-proxmox is available in nexus

Description:

An Edge deployment should default to use artifacts from nexus, this allows us to also support Airgap environments.

The opnsense role requires the packer-plugin-proxmox and it is not found in nexus, instead it is pulled from upstream. This will break in airgap.

Need to ensure artifact needed is available in nexus and verify deployment uses nexus artifact.

TASK [opnsense : Set Proxmox Module url] ***************************************
Thursday 21 August 2025  22:09:12 +0000 (0:00:01.075)       0:00:08.515 *******

ok: [babu] => changed=false
  ansible_facts:
    ProxmoxModule_url: https://github.com/hashicorp/packer-plugin-proxmox/releases/download/v1.1.8/packer-plugin-proxmox_v1.1.8_x5.0_linux_amd64.zip

Acceptance Criteria:

• Ensure artifact needed is available in nexus
• Deployment uses nexus artifact