Update the `supported_os` local variable in `01-virtual-machines.tf` to
reflect current provisioning requirements. This change removes `centos`
and adds `ipfabric` to the set of allowed operating system templates.
- Add `qemu-guest-agent` enable/start command to `user-data.yml.tftpl` to ensure the agent is active immediately after provisioning.
- Set `stop_on_destroy = true` in the Proxmox VM resource definition to ensure graceful shutdown during Terraform destroy operations.
The commit rephrases the README to focus on Cloud-Init setup and removes
unused Ansible code, making Tailscale configuration automatic.
Subject line: Replace Ansible with automated Cloud-Init configuration
Body: Refactors infrastructure bootstrapping to leverage Cloud-Init
instead of Ansible for initial VM setup, particularly with respect to
Tailscale installation and authentication.
This simplifies the architecture by: - Removing manual post-provisioning
Ansible steps - Automating Tailscale setup via Cloud-Init - Updating
documentation to reflect new workflow
