catalog: add virig_5imus_4cams (hosted, no results yet) + sensor used_in

rename virig-{3,4}cams -> virig-4imus-{3,4}cams (add IMU count)

datasets.json: tum_rs/double_sphere license wording (confirmed unlicensed, recipe-only)

datasets.json: Blackfly model filled (BFS-U3-16S2M, IMX273)

datasets.json: dataset catalog (per-physical-dataset hardware/board/license metadata, generated by catalog.py)