[Feature request] Omnia Modernization

After chatting with @richardhenwood-dell about the idea of an API he got me thinking. Today operating an Omnia cluster means SSHing to the OIM, editing files under `input/`, and running `ansible-playbook` which makes it hard to drive Omnia from CI/CD, monitoring webhooks, or portals, and leaves no job history or audit trail.

We might consider developing an optional omnia-api container in the OIM stack exposing the existing playbooks through a REST API (perhaps via [ansible-runner](https://ansible.readthedocs.io/projects/runner/)), with async jobs and a published OpenAPI spec. The playbooks stay the implementation and the current workflow keeps working unchanged.

What do others think? @i3igpete @lwilson @sujit-jadhav

Start by reviewing the OIM stack, the files under input/, and the existing Ansible playbooks, then examine whether ansible-runner fits the proposed execution model. The issue needs a concrete scope for the optional API, asynchronous jobs, audit history, and OpenAPI specification before implementation can be considered done.

Written by the indexing model from the issue text.