Add MAC to each board [For FW & ADJ-Validator]

[JavierRibaldelRio]

Add a board_mac field to the board configuration.

Example:

{
  "board_id": 1001,
  "board_ip": "192.168.1.10",
  "board_mac": "AA:BB:CC:DD:EE:FF"
}

The ADJ Validator should only check that board_mac is a valid MAC address, FW code generation should also use it.

Incorrect MAC addresses caused communication bugs during EHW 2026, so validating them in the ADJ would help prevent similar issues.