Replace wkhtmltox for PDF generation
The safety form PDFs are currently generated using python3-pdfkit which wraps wkhtmltox. We already have to download the wkhtmltox author's packages rather than using the distro packages, as they statically link some fixes to Qt. The author has stopped work on the project as of 2023 and archived it. We should therefore move to something else. Weazyprint looks like a possibility.