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.