text: Title: Wrong skeleton structure issue when trying to load a svg skeleton file
  Body: ### Actions before raising this issue
  
  - [X] I searched the existing issues and did not find anything similar.
  - [X] I read/searched [the docs](https://docs.cvat.ai/docs/)
  
  ### Steps to Reproduce
  Hi folks, 
  
  I created a skeleton in a project using CVAT self hosted version and then exported it into a svg file.
  
  Then I created a new project and tried to upload my previous svg file as a new skeleton but I got "Wrong skeleton structure" error.
  
  Do you have any idea how to fix this issue ?
  
  Thanks a lot
  
  ![Error](https://github.com/user-attachments/assets/c54f6ac3-8c7f-4337-97aa-26156c31fc65)
  
  
  
  ### Expected Behavior
  
  The upload function should load my svg file as a new skeleton
  
  ### Possible Solution
  
  _No response_
  
  ### Context
  
  _No response_
  
  ### Environment
  
  CVAT installed on Windows laptop
  Ubuntu and Docker Desktop