Add support for Lilygo T-CAN485

[dassader]

What Changed

• Added support for the Lilygo T-CAN485 board (SYSTYPE=4)
• Added way to disabled OTA (otaHost/otaFilename = "none")
• Fixed configs for boards with single can bus

LILYGO T-CAN485 Pin Mapping

GPIO26 -> Can RX
GPIO27 -> Can TX
GPIO23 -> Can can transceiver standby mode (LOW to avoid standby)
GPIO16 -> Step-up converter EN (HIGH to enable 5V power)
GPIO4 -> WS2812B data

Board Type Configuration

Run this command in the device console:

SYSTYPE=4

Fix for Single-CAN Boards

Fixed CAN settings application via GVRET for boards that expose only CAN0:

• added safe checks for presence of CAN1,
• CAN1 config packets are now ignored safely on single-CAN boards,
• removed the risk of applying settings to a non-existent CAN bus