Python 3.13: 80 failing tests

Hi 👋

After disabling hanging tests (see #613 (closed)) I ran into 80 failing tests.

• postorius-1.3.13-2-x86_64-build.log
• postorius-1.3.13-2-x86_64-check.log

Many appear to be the same as mailmanclient#78 (closed) but there are also others, e.g.

FAILED src/postorius/tests/mailman_api_tests/test_anonymous_subscribe.py::AnonymousSubscribeTest::test_anonymous_subscribe - AssertionError: 'danger' != 'success'

FAILED src/postorius/tests/mailman_api_tests/test_user.py::TestManageUser::test_delete_user_multiple_emails - urllib.error.HTTPError: HTTP Error 400: User already exists: user@example.com