Implement sending email notifications in background mode

Для оптимизации процессов необходимо осуществлять отправку нотификаций в фоновом режиме

The issue mentions sending email notifications in the background but does not specify the current notification system or which emails to move. Look for existing email-sending code, likely in Django views or signals. Research Django's Celery or RQ for background tasks, and check the project's configuration for any existing task queue setup. 'Done' means emails are queued and sent asynchronously without blocking the main request.

Written by the indexing model from the issue text.