业务更名为撞车并切换crash路由

用户可见文案与页面/API路径改为撞车与crash，保留mohong表与权限码兼容；移动端入口去掉租/撞图标。

backend/internal/modules/file/handler.go

@@ -70,7 +70,7 @@ func (h *Handler) writeObject(c *gin.Context, publicOnly bool) {
 		!strings.HasPrefix(key, "avatar/") &&
 		!strings.HasPrefix(key, "payment-cert/") &&
 		!strings.HasPrefix(key, "announcement/") &&
-		!strings.HasPrefix(key, "mohong/") {
+		!strings.HasPrefix(key, "mohong/") && !strings.HasPrefix(key, "crash/") {
 		response.Error(c, http.StatusNotFound, "not_found", "文件不存在或暂不可访问")
 		return
 	}