Update PDF generation library

[circumspect]

Alternatives

• Pyfpdf2: (mostly) maintains compatibility with the current code, which is built on pyfpdf, but is actively maintained.
• Pypdf: also actively maintained, but would require an extensive rewrite of the export functionality.

Pyfpdf2 seems like the better option, as the PDF export function is very large and moving to pypdf would consume a lot of time.

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TODO:

• [ ] Update font definitions to avoid fpdf2 ValueErrors