Refactor golden image handling in backup upload process</message>

<message>Update the _set_golden_from_path function to improve the handling of existing golden image files. Replace the existing unlink logic with a more robust method that safely removes files or broken symlinks using the missing_ok parameter. This change enhances the reliability of the backup upload process by ensuring that stale references are properly cleared before setting a new golden image path.

emmc-provisioning/dashboard/app.py

@@ -1175,8 +1175,8 @@ def api_backups_upload():
 def _set_golden_from_path(path):
     """Set golden image to point to given path (file in backups or cloudinit dir)."""
     GOLDEN_IMAGE.parent.mkdir(parents=True, exist_ok=True)
-    if GOLDEN_IMAGE.exists():
-        GOLDEN_IMAGE.unlink()
+    # Remove existing file or symlink (including broken symlink; exists() is False for broken links)
+    GOLDEN_IMAGE.unlink(missing_ok=True)
     path_resolved = path.resolve()
     try:
         path_resolved.relative_to(BACKUPS_DIR.resolve())