feat(VL53L4CD): 增加偏移校准支持并固化44mm安装偏移

- 新增 vl53l4cd_set_offset/get_offset/calibrate_offset
- main 支持开机自动校准或启动时写回固定偏移
- 当前44mm哑光目标校准结果 offset=-9mm
- 同步更新 README 与 CHANGES

Src/main.c

@@ -78,6 +78,19 @@ int main(void)
 #endif
 
     if (vl53l4cd_init()) {
+#if VL53L4CD_AUTO_CALIB == CFG_ENABLE
+        int16_t cal_offset = 0;
+
+        if (vl53l4cd_calibrate_offset(VL53L4CD_CALIB_TARGET_MM,
+                                      VL53L4CD_CALIB_SAMPLES,
+                                      &cal_offset)) {
+            printf("VL53L4CD offset calibrated: %d mm\r\n", cal_offset);
+        } else {
+            printf("VL53L4CD offset calibration failed\r\n");
+        }
+#else
+        (void)vl53l4cd_set_offset(VL53L4CD_CALIB_OFFSET_MM);
+#endif
         vl53l4cd_start_ranging();
         printf("VL53L4CD ready\r\n");
     } else {