add proxmox nfs shares

variables.nix

@@ -103,10 +103,14 @@
       subpath = "raspi/volumes";
       mountpoint = "/mnt/raspi-backup";
     };
-    proxmoxVolumes = {
+    proxmoxIsos = {
       subpath = "proxmox/iso";
       mountpoint = "/mnt/iso";
     };
+    proxmoxPxeImages = {
+      subpath = "proxmox/pxe-images";
+      mountpoint = "/mnt/pxe-images";
+    };
   };
 
   # The Raspberry Pi's own NFS export — not under storageRoot/nfsServerHost,