Replace compile-time orientation enum/macro approach with a general
3x3 rotation matrix IMU2BODY_ROTATION. User fills in the matrix
according to actual IMU mounting orientation. Matrix must be a proper
rotation (det = +1) to preserve right-handed coordinate system.
Support NORMAL, YAW_180, ROLL_180, PITCH_180 presets selected at compile
time by IMU_MOUNT_ORIENTATION macro. Replaces direct BMI088-to-INS
assignment with IMU_Mount_Correct() for sign flip and axis swap.
SkyLiCoder