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/esp_now_proto.h

@@ -14,6 +14,11 @@ esp_err_t esp_now_proto_encode(const alox_EspNowMessage *msg, uint8_t *buf,
 esp_err_t esp_now_proto_decode(const uint8_t *data, size_t len,
                                alox_EspNowMessage *msg);
 
+/** Decode messages that carry EspNowSlavePresence (mac callback required). */
+esp_err_t esp_now_proto_decode_with_mac(const uint8_t *data, size_t len,
+                                        alox_EspNowMessage *msg,
+                                        uint8_t mac_out[6]);
+
 void esp_now_proto_setup_presence_encode(alox_EspNowSlavePresence *presence,
                                          const uint8_t mac[6]);