Fix: ensure disk is unmounted before partitioning and use sudo for reboot

iridium_installer/ui/window.py

@@ -247,7 +247,8 @@ class InstallerWindow(Adw.ApplicationWindow):
             def on_restart(b):
                 import subprocess
                 try:
-                    subprocess.run(["systemctl", "reboot"])
+                    # Use sudo since we might be running as liveuser
+                    subprocess.run(["sudo", "systemctl", "reboot"])
                 except Exception as e:
                     print(f"Failed to reboot: {e}")
                     self.close()