Improve handling of deleted user account

[norbertschuler]

If a user deleted his account and is still logged into the app, the API responds with 303 which currently leads to the sign up page, but the sign up process fails as the authorization token is no longer valid of course.

Also the local species data is not deleted, so after the user signs up again the local species data if getting edited is raising 500 errors with the backend trying to store this no more existing data in the backend.

This is an edge case with less priority.