refactor: move centering to 3mf gen

src/components/md-token-viewer.tsx

@@ -51,14 +51,6 @@ export default function MdTokenViewer(props: TokenViewerProps) {
 
       // 3MF 文件可能返回一个 Group，包含多个 Mesh
       group = object instanceof THREE.Group ? object : new THREE.Group().add(object);
-
-      // 计算边界框并居中
-      const box = new THREE.Box3().setFromObject(group);
-      const center = box.getCenter(new THREE.Vector3());
-      group.position.x = -center.x;
-      group.position.y = -center.y;
-      group.position.z = -center.z;
-
       group.rotateX(Math.PI);
 
       // 为每个 mesh 启用原始颜色