Add optional BMA456 accelerometer init on shared I2C bus.

Probe and configure the sensor when present; log and continue boot if
init fails so boards without BMA456 still run normally.

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

main/bosch456.h

@@ -0,0 +1,15 @@
+#ifndef BOSCH456_H
+#define BOSCH456_H
+
+#include "driver/i2c_types.h"
+#include "esp_err.h"
+
+#define TOUCH_1 9
+#define TOUCH_2 8
+
+#define BMA456_ADDRESS 0x18
+
+/** Initialize BMA456 on the shared I2C bus. Returns ESP_OK or logs and skips sensor use. */
+esp_err_t init_bma456(i2c_master_bus_handle_t bus_handle);
+
+#endif