- Fix I2C pins in variant.h (GPIO21/22 → GPIO4/5 per datasheet)
- Fix GPS UART pins in platformio.ini (UART0 1/3 → UART1 21/19)
- Fix radio_set_tx_power signature (uint8_t → int8_t)
- Remove conflicting duplicate defines between variant.h and Board.h
(P_LORA_BUSY was RADIOLIB_NC vs 13, ADC_MULTIPLIER was 1.85 vs 5761)
- Remove stale LoRa/WisBlock defines from variant.h (Board.h is
authoritative)
- Remove "ethernet" and "can" from board JSON connectivity
- Use static SPIClass for radio init (matches Heltec V3 convention)
- Remove build_unflags=-Os (keep size optimization for 4MB flash)
Verified against RAK11200/RAK13300 datasheets