Add esp_now_messages.proto with EspNowMessage types, encode/decode helpers,
and Makefile targets to regenerate firmware and UART schemas together.
Co-authored-by: Cursor <cursoragent@cursor.com>
Centralize command dispatch over a FreeRTOS queue so UART and future
ESP-NOW transports can register handlers; implement the protobuf VERSION
command with framed nanopb responses including build git hash.
Co-authored-by: Cursor <cursoragent@cursor.com>
