Try both stock and K2-Improvements file paths for material_box_info.json

K2-Improvements firmware moves the file from
/usr/data/creality/userdata/box/ to /mnt/UDISK/creality/userdata/box/.
Try the K2-Improvements path first, fall back to stock path.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>