Add option to purge user data

[mateuszmigas]

Is your feature request related to a problem? Please describe. User might want to clear all data.

Describe the solution you'd like In the general settings tab, add a new button to purge user data. Warn the user that this action cannot be reversed. This action should:

1. Clear blobs from the database.
2. Clear the application state.
3. Clear API keys.

Describe alternatives you've considered N/A

Additional context N/A