meta/stats.json: aggregate LeRobot v2.1 stats (replaces openpi norm_stats mis-uploaded here)

Remove top-level stats.json (moved to meta/)

Move stats.json to meta/ (LeRobot visualizer convention)

Add stats.json at top level (norm_stats used for deployment)

Add pi05_xarm_peg norm_stats used for deployment

Upload peg_black_v2 LeRobot v2.1 dataset (215 eps, task=pick up the black peg and insert it)

initial commit