Fledge IoT Gateway Backup Restore Tar Path Traversal

Fledge's backup-restore upload handler, upload_backup() (python/fledge/services/core/api/backup_restore.py), calls tarfile.extractall(temp_path) on an admin-uploaded tar archive with no filter argument and no per-member path validation. A crafted tar archive containing member names with `../` path components extracts files outside the intended temporary directory, allowing arbitrary file writes anywhere on the filesystem reachable by the Fledge process. Requires the admin role (@has_permission("admin")).