CONF Lorenz_IJCB_2026/IDIAP Foundation Models for Face Presentation Attack Detection: A Unified Linear-Probing Benchmark Lorenz, Peter George, Anjith Marcel, Sébastien EXTERNAL https://publications.idiap.ch/attachments/papers/2026/Lorenz_IJCB_2026.pdf PUBLIC IEEE International Joint Conference on Biometrics (IJCB) 2026