Test for old links to continue existing

We should add a test that ensures that all redirects and permalinks before the hugo migration will continue to work after the hugo port.

I wrote a script that generates a list of expected output files. This needs to be run in a completely checked out root of a website repo. [links.py](https://github.com/user-attachments/files/29468816/links.py) resulting in [links.txt](https://github.com/user-attachments/files/29469047/links.txt)

An alternative would be to capture all html files of a current build.

This could be stored as a txt somewhere.

After the build, we then ensure that all these files are still present in the output.

Start with links.py and the generated links.txt, using them in a completely checked-out website repository. Run the Hugo build and determine where the expected paths should be stored or checked; done means every listed redirect and permalink still has a corresponding output file after the build.

Written by the indexing model from the issue text.