- Consolidate unit of work implementation with NotificationUnitOfWork.
- Refactor repositories to use NotificationBaseRepository for consistency.
- Simplify request handlers by removing IUnitOfWork dependency.
- Update related tests and service registration.
- Add TestSmtpCommand and TestSmtpHandler for ad-hoc smtp testing without saving
- Add POST /admin/channels/test-smtp endpoint accepting raw smtp settings
- Show Test button on both Create and Edit forms
- Test reads current form values so channel can be tested before saving