Publishes the RV's 12V LiFePO4 house battery to HA via MQTT discovery
(pack voltage, 4 cell voltages, current, SOC, BMS/battery temp, status).
Connects over the battery's BLE HM-10 UART module (service ffe0/char
ffe1, no pairing) using bleak; protocol reverse-engineered from the
com.lithionics.bms Android app's own BLE/parsing code.
Deliberately named li3/ and van-li3-battery, not battery/van-battery —
that name is reserved for the host's own AC/UPS power-supply monitor
(different hardware, unrelated concern).
Self-heals a bluetoothd discovery-state wedge (Discovering stuck "yes",
connects failing with le-connection-abort-by-local) that shows up after
repeated failed connects to this device on the Pi's onboard adapter: the
daemon retries scan/connect internally (MQTT session and HA entities
stay up across retries) and restarts bluetooth.service itself after 3
consecutive scan failures, rate-limited to once per 5 min.
