Since we don't use parents=True anymore to create the folders (which I
think is good), we now need to ensure that those exist.

So

1. when fietsboek starts up, we create those folders, and
2. when we delete them in the tests, we recreate them.

This doesn't check any content of the PDF, but ensures that running
typst does not produce an error.

matplotlib procudes a lot of lines for the font manager, which really
clutter the log output for everything else.

Otherwise Postgres does not let us drop the tables and hangs forever

Previously, we had it session-scoped, which meant that the app was
created once for all tests. This doesn't allow us to play with different
settings however, such as disabling account registration or image
uploads and testing that.

Now, the fixtures are module scoped, which means that we still save on
prepare/teardown time a bit, but we're also a bit more flexible. By
making new test modules, we can test different settings there.

See if it works, it might be handy for other tests in the future as
well.

They caused issues because they might not have created the database
tables or the data directory. Since the cleanup job runs globally after
every test, it should take that into consideration and not error out.