fix(terraform): Configure storage for LINSTOR cluster topology

Storage configuration changes:
- Add full_clone=true for better LINSTOR compatibility
- Add replicate=1 to disk config for k3s servers on LINSTOR
- Configure etcd-witness to use local-lvm storage on thinkpad
- Add etcd_witness_storage_pool variable with local-lvm default

Fixes:
- etcd-witness now uses local storage since thinkpad is LINSTOR controller only
- k3s-server-1 and k3s-server-2 use LINSTOR replicated storage on acemagician/elitedesk
- Explicit replication flag helps LINSTOR create resources correctly

terraform/pve3/variables.tf

@@ -53,6 +53,12 @@ variable "storage_pool" {
   type        = string
 }
 
+variable "etcd_witness_storage_pool" {
+  description = "Proxmox storage pool for etcd witness VM disk (thinkpad uses local storage)"
+  type        = string
+  default     = "local-lvm"
+}
+
 variable "snippets_storage" {
   description = "Proxmox storage for cloud-init snippets"
   type        = string