Also move shared pytest fixtures to conftest.py

https://docs.python.org/3/library/random.html#random.choices

Also randomly generate an auth_token now.

https://github.com/PyCQA/pylint/issues/2108

Also tested this by translating a little bit to German and Spanish.

Source: https://code.briarproject.org/briar/briar/blob/release-1.1.7/briar-android/artwork/logo_circle.svg

Also listen on other enter button and empty entry after sending.

Co-Authored-By: ialokim <ialokim@t-online.de>

Inspired by
https://code.briarproject.org/grote/briar-cli-python-demo/blob/8ced7b9f37e6ee59dac6042c9bcf21c54c648e9e/briar-cli.py.