Fledge IoT Gateway Backup Restore OS Command Injection via Tar Member Filename

Fledge's backup-restore upload handler, upload_backup (python/fledge/services/core/api/backup_restore.py), takes the first extracted tar member's filename (tar_file_names[0]) and builds a shell command via string formatting. Because os.system invokes a shell and no quoting (shlex.quote, list-form subprocess) is applied, an admin uploading a crafted backup archive achieves arbitrary OS command execution.