refuse to (fail to) calibrate shake sensitivity while in sleep mode

[lmamane]

No description provided.

[github-actions]

Build size and comparison to main:

Section	Size	Difference
text	374768B	176B
data	948B	0B
bss	63504B	0B

[mark9064]

This all looks good, but I think the calibrating variable should be refactored into a state enum instead as it's currently somewhat unintuitive and the 255 value doesn't help. Perhaps something like States {Idle, PrepareToCalibrate, Calibrating, CalibrationDisabled}? These probably aren't the best names, I haven't thought about them much. Hopefully you get the idea though