Add command queue dispatcher and VERSION UART handler.

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>

main/uart.h

@@ -1,8 +1,10 @@
 #ifndef UART_H
 #define UART_H
 
+#include "esp_err.h"
 #include "freertos/idf_additions.h"
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 #define UART_NUM UART_NUM_1
 #define UART_BUF_SIZE 256
@@ -38,5 +40,6 @@ typedef struct {
 void init_uart(QueueHandle_t cmd_queue);
 void uart_read_task(void *param);
 bool parse_uart_byte(uint8_t byte, uart_packet_t *p);
+esp_err_t uart_send_framed(const uint8_t *payload, size_t len);
 
 #endif