[Feature] 应该提醒用户修改默认的邮箱和密码

### Description / 功能描述

很多人会不修改邮箱和密码一直使用默认的邮箱和密码，如果暴漏在公网上这将会非常危险
建议如果使用默认账号登录时，登录成功后弹窗提醒用户修改密码或是强制修改密码

### Motivation / 请求动机

有遇到过许多这类型的用户

### Miscellaneous / 其他

_No response_

### Contribution / 贡献代码

- [x] I am interested in contributing a PR for this! / 我乐意为此提交代码并发起 PR！

No files or tests are named. Start by tracing the default-account login entry point and how successful authentication is handled; clarify whether the completed behavior is a warning dialog or a mandatory password change, then verify that users with default credentials are prompted after login and other users are unaffected.

Written by the indexing model from the issue text.