Cart is empty after page reload

After adding an item to the cart, then clicking on cart, the item appears as expected. But when you reload the web page in the browser the cart becomes empty.

Also, after adding an item to the cart, the button becomes "REMOVE FROM CART". Then when that web page is reloaded, the same button reverts to "ADD TO CART".

未指定文件或测试。先重现重新加载时的行为，然后跟踪 React 购物车状态如何通过 Apollo/GraphQL 客户端存储和恢复。完成标准是：重新加载页面后，已添加的项目及其 REMOVE FROM CART 状态仍然保留。

由索引模型根据 Issue 内容生成。