The NAU7802 ADC returns a stale max-scale value (0x7FFFFF) on its
first conversion after power-up, polluting the moving average and
making the initial weight report wildly inaccurate. Flush the first
reading during init().
Also extract both hardware drivers out of diagnostic scripts into
proper daemon modules:
- NAU7802 scale driver: scripts/scale_diag.py -> daemon/nau7802.py
- PN5180 NFC driver: scripts/read_tag.py -> daemon/pn5180.py
The production daemon was importing driver classes from test scripts
since the original SpoolBuddy commit. Diagnostic scripts now import
from the driver modules. Removed the sys.path hack from main.py.
Keybored