Reconsider weasyprint==67.0 hard pin

[patdhlk]

Found in: #121

Problem

weasyprint was changed from >=67.0 to ==67.0 in [project.dependencies]. An exact pin in a library's production dependencies prevents users from:

• Receiving bug fixes and security patches (e.g. CVE-2025-68616 fixed in 68.0)
• Using other packages that may require a different weasyprint version

WeasyPrint 68.0 does have breaking changes (deprecated default_url_fetcher, changed redirect handling), so a constraint is justified.

Action needed

Either:

• Document the specific reason for the hard pin, or
• Relax to a bounded range like >=67.0,<69 which avoids the 68.0 breakage while being less restrictive

[kreuzberger]

From my side there was no specific reason for the hard pin, its just left from the issue that the weasyprint process crashed reproducable on windows. Reason was the wrong @font_face. I tried several exact reasons of weasyprint to see if the reason could be a specific weasyprint version, this hard pin is just a leftover that i forgot to "remove".