fix: UEFI VMs trying PXE boot instead of disk when no ISO attached

OVMF (UEFI BIOS) defaults to PXE boot when no explicit boot order is
set. SeaBIOS defaults to disk, so this was never noticed on legacy VMs.
When a user removes the ISO after installing their OS, the VM would
try PXE → fail → hang at TianoCore screen instead of booting from disk.

Fix: always set -boot order explicitly. With boot media: order=dc
(CD first). Without: order=c (disk first).

Author: Paul C

src/vms/manager.rs

@@ -1241,9 +1241,11 @@ impl VmManager {
             }
         }
 
-        // Boot order: boot media first (for installation), then disk
+        // Boot order: always explicit so OVMF (UEFI) doesn't default to PXE
         if has_boot_media {
-            cmd.arg("-boot").arg("order=dc");
+            cmd.arg("-boot").arg("order=dc");  // CD/USB first, then disk (installation)
+        } else {
+            cmd.arg("-boot").arg("order=c");   // Disk first (normal boot)
         }
 
         write_log(&format!("Launching QEMU: VNC :{} (port {}), KVM: {}", vnc_num, vnc_port, kvm_available));