[Question] <title>数据库账号有效期监控

### Question

1、数据库监控功能配置的账号，过期情况下，报警消息应该提示账号过期，而非数据库无法连接。
2、监控指定账号的有效期，过期提前7天、3天、已过期，发提示消息

The issue names no files, tests, or entry points. Start by locating the database monitoring account-validation and alert-notification paths, then determine how account expiry is distinguished from connection failure. Done means expiry is reported accurately and notifications are sent 7 days before expiry, 3 days before expiry, and after expiry.

Written by the indexing model from the issue text.