Migrate runner manager from Proxmox VM to lab k8s

The interim runner manager runs on a Proxmox VM (decision recorded in #1). Once the lab Talos cluster and GitOps are up (lab#3, lab#4), move the manager into k8s.

The durable pieces carry over unchanged: config.toml (fleeting AWS plugin, IdleCount=0, instance types), the AWS IAM role, the AMI bake, and job routing. Scope here is replacing the VM provisioning (OpenTofu) and install role (Ansible) with a k8s deployment, likely the GitLab Runner Helm chart running the docker-autoscaler executor.

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