- Remove global `RootUserEmail` variable
- Modify channel testing and user notification methods to use `GetRootUser()`
- Update user cache and notification service to use more consistent user base type
- Add new channel test notification type
- Introduce AutomaticDisableKeywords setting to dynamically control channel disabling
- Implement AC search for matching error messages against disable keywords
- Add frontend UI for configuring automatic disable keywords
- Update localization with new keyword-based channel disabling feature
- Refactor sensitive word and AC search logic to support multiple keyword lists
