Various fixes and improvements

[NicoPennec]

Problem

• A supervisor should not be able to modify playlists unless they created them.
• In the Add Thumbnails form, when a file doesn't match the pattern, it isn't explicitly indicated.
• The component behaves inconsistently when the user cancels their file selection (native cancel button). It clears the selection but still displays the file as selected.
• The CI workflow could be executed more quickly.
• Some npm dependencies are outdated.

Solution

• Allow a supervisor to modify only their playlists.
• Improve the Add Thumbnails form by listing invalid files.
• Fix the File Upload reset behavior on user cancel.
• Improve the CI workflow:
  • Improve unit test config with threading.
  • Parallelize some job executions.
• Bump npm dependencies.