proxmox: add VM automation with OpenTofu and Ansible

Add automated workflow for building and deploying NixOS VMs on Proxmox including template2 host configuration, Ansible playbook for image building/deployment, and OpenTofu configuration for VM provisioning with cloud-init.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -44,6 +44,15 @@ nix develop
 
 Secrets are handled by sops. Do not edit any `.sops.yaml` or any file within `secrets/`. Ask the user to modify if necessary.
 
+### Git Commit Messages
+
+Commit messages should follow the format: `topic: short description`
+
+Examples:
+- `flake: add opentofu to devshell`
+- `template2: add proxmox image configuration`
+- `terraform: add VM deployment configuration`
+
 ## Architecture
 
 ### Directory Structure
@@ -143,6 +152,57 @@ Configured in `/system/autoupgrade.nix`:
 - Auto-reboot after successful upgrade
 - Systemd service: `nixos-upgrade.service`
 
+### Proxmox VM Provisioning with OpenTofu
+
+The repository includes automated workflows for building Proxmox VM templates and deploying VMs using OpenTofu (Terraform).
+
+#### Building and Deploying Templates
+
+Template VMs are built from `hosts/template2` and deployed to Proxmox using Ansible:
+
+```bash
+# Build NixOS image and deploy to Proxmox as template
+nix develop -c ansible-playbook -i playbooks/inventory.ini playbooks/build-and-deploy-template.yml
+```
+
+This playbook:
+1. Builds the Proxmox image using `nixos-rebuild build-image --image-variant proxmox`
+2. Uploads the `.vma.zst` image to Proxmox at `/var/lib/vz/dump`
+3. Restores it as VM ID 9000
+4. Converts it to a template
+
+Template configuration (`hosts/template2`):
+- Minimal base system with essential packages (age, vim, wget, git)
+- Cloud-init configured for NoCloud datasource (no EC2 metadata timeout)
+- DHCP networking on ens18
+- SSH key-based root login
+- `prepare-host.sh` script for cleaning machine-id, SSH keys, and regenerating age keys
+
+#### Deploying VMs with OpenTofu
+
+VMs are deployed from templates using OpenTofu in the `/terraform` directory:
+
+```bash
+cd terraform
+tofu init     # First time only
+tofu apply    # Deploy VMs
+```
+
+Configuration files:
+- `main.tf` - Proxmox provider configuration
+- `variables.tf` - Provider variables (API credentials)
+- `vm.tf` - VM resource definitions
+- `terraform.tfvars` - Actual credentials (gitignored)
+
+Example VM deployment includes:
+- Clone from template VM
+- Cloud-init configuration (SSH keys, network, DNS)
+- Custom CPU/memory/disk sizing
+- VLAN tagging
+- QEMU guest agent
+
+OpenTofu outputs the VM's IP address after deployment for easy SSH access.
+
 ### Adding a New Host
 
 1. Create `/hosts/<hostname>/` directory