feat(proxmox): Proxmox VM template + Terraform/OpenTofu VM creation

Manual, documented bare-metal Proxmox install + cloud-init template build
(deliberately not automated — a fragile one-time step). Terraform/OpenTofu
config creates rn-platform-01/rn-lab-host-01 from that template via the
bpg/proxmox provider, with configurable (not hardcoded) VM sizing.

Validated: tofu fmt, tofu init -backend=false (real provider download),
tofu validate -> Success. No paid state backend required (local state).

infra/terraform/versions.tf

@@ -0,0 +1,23 @@
+terraform {
+  required_version = ">= 1.5.0"
+  required_providers {
+    proxmox = {
+      source  = "bpg/proxmox"
+      version = "~> 0.60"
+    }
+  }
+
+  # Local state by default — no paid backend required. Uncomment for remote state once/if
+  # that's wanted; not needed to use this module.
+  # backend "s3" {
+  #   bucket = "rootnode-terraform-state"
+  #   key    = "production/terraform.tfstate"
+  #   region = "auto"
+  # }
+}
+
+provider "proxmox" {
+  endpoint  = var.proxmox_api_url
+  api_token = var.proxmox_api_token
+  insecure  = var.proxmox_tls_insecure
+}