希望增加删除收藏的 API

客户端可以增加删除收藏的功能。这样如果用户不小心把一个并不想看的番标记了想看，可以删除这个标记。

Start by locating the existing API endpoint and data model for adding a favorite. Trace how a favorite is identified and removed, then check the current API tests or request examples. Done means clients can delete an unintended favorite reliably and the behavior is covered by the API's existing test or documentation pattern.

Written by the indexing model from the issue text.