Detect under-voltage on GPIO1/11, persist UV state in NVS, enter a minimal
power mode without ESP-NOW, and recover after charge; expose LED mode 6
battery-low for host testing via goTool.
Co-authored-by: Cursor <cursoragent@cursor.com>
Slaves report pack voltages every 30s; the master caches them for fast
BATTERY_STATUS reads. goTool exposes REST/WebSocket and shows values in
the dashboard, with a nanopb fix so optional lipo submessages encode.
Co-authored-by: Cursor <cursoragent@cursor.com>
TODO: Hardware pinning in powerpod.h (TASTER_GPIO, V_LIPO_1/2_GPIO) does not
match final hardware yet — verify against schematic before production.
Co-authored-by: Cursor <cursoragent@cursor.com>