Remove tailscale auth/bootstrap from cloud-init and workflows, keeping VM provisioning focused on core network behind pfSense while preserving SSH key cloud-init setup.
Remove guest-agent enrollment workflow, pass TS auth key through Terraform variables/secrets, and run tailscale up with tag:k8s during cloud-init bootstrap alongside SSH key injection.
- Point clone_template to nixos-template and trim cloud-init to Nix-safe hostname/DNS only
- Remove SSH/Tailscale cloud-init variables and workflow secret dependencies
- Add reusable NixOS template-base config with bootloader, Tailscale, fish, and utility packages