Feature Request: Notification History with Soft Delete and Auto-Pruning

**Is your feature request related to a problem? Please describe.**
Accidental deletion of notifications in Gotify results in permanent loss of information, as there is currently no way to recover them. This can be problematic when reviewing important alerts or messages.

**Describe the solution you'd like**
Implement a "Notification History" feature that acts as a soft delete mechanism. When a notification is deleted, instead of immediate removal, it should be moved to this history section.

Furthermore, introduce an auto-pruning functionality for the Notification History. This allows users to configure a retention period (e.g., 30 days) after which older notifications are automatically and permanently deleted. Users should be able to customize this retention period to suit their needs.

Benefits:

- Data Recovery: Enables recovery of accidentally deleted notifications.
- Audit Trail: Provides a historical record of notifications for review and troubleshooting.
- Storage Management: Auto-pruning ensures efficient storage usage by removing outdated notifications.
- User Control: Customizable retention period gives users control over the history's lifespan.

**Describe alternatives you've considered**
Using email notifications as a workaround, leveraging the email client's trash/archive functionality. However, this introduces reliance on a separate system and may not be suitable for all notification types.

**Additional context**
NA