mieru Files

1. Add user hint function to accelerate decrypt when the number of users in proxy server is high (issue [#264]).
2. Allow proxy server to refuse proxy client when user hint is not provided.

The length of a username or a password must be less than or equal to 64 bytes.

1. 新增用户提示功能，在代理服务器用户数量多时加快解密速度。
2. 允许代理服务器在客户端未提供用户提示时拒绝服务。

用户名或密码的长度不得大于 64 个字节。