fix: upload one ISO per PVE version, not per node

Changed Terraform ISO resource from for_each=pve_instances (per-node)
to for_each=pve_isos (per-version). With HTTP answer server, both
nodes of the same version share the same generic ISO.

New pve_isos variable maps version to ISO path. pve_instances now
has pve_version field instead of iso_local_path. VMs reference
their version's ISO via auto_iso[each.value.pve_version].

Updated run-integration.sh tfvars generation and -target flags
for both provision and cleanup to use the new schema.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/infrastructure/main.tf

@@ -24,13 +24,14 @@ provider "docker" {
 }
 
 resource "proxmox_virtual_environment_file" "auto_iso" {
-  for_each     = var.pve_instances
+  for_each     = var.pve_isos
   content_type = "iso"
   datastore_id = var.iso_storage
   node_name    = var.target_node
+  overwrite    = true
 
   source_file {
-    path = each.value.iso_local_path
+    path = each.value
   }
 }
 
@@ -69,7 +70,7 @@ resource "proxmox_virtual_environment_vm" "nested_pve" {
   }
 
   cdrom {
-    file_id   = proxmox_virtual_environment_file.auto_iso[each.key].id
+    file_id   = proxmox_virtual_environment_file.auto_iso[each.value.pve_version].id
     interface = "ide2"
   }