add cleanup to podman container update

modules/podman.nix

@@ -44,6 +44,14 @@ let
     done
 
     echo "Container update scan complete!"
+
+    # Clean up dangling images
+    echo "Cleaning up dangling images..."
+    if podman image prune -af; then
+      echo "Image cleanup complete!"
+    else
+      echo "Warning: Image cleanup failed"
+    fi
   '';
 in
 {