Add accelerometer deadzone via UART and ESP-NOW.

Filter BMA456 logs by configurable LSB threshold; master can set deadzone
for local sensor or slaves using ACCEL_DEADZONE (UART) and ESP-NOW broadcast
until unicast delivery is restored.

Co-authored-by: Cursor <cursoragent@cursor.com>

main/powerpod.c

@@ -1,5 +1,6 @@
 #include "app_config.h"
 #include "cmd_handler.h"
+#include "cmd_accel_deadzone.h"
 #include "cmd_client_info.h"
 #include "cmd_version.h"
 #include "esp_now_comm.h"
@@ -144,6 +145,7 @@ void app_main(void) {
     init_uart(cmd_queue);
     cmd_version_register();
     cmd_client_info_register();
+    cmd_accel_deadzone_register();
   }
 
   uint8_t current_digit = 10;