Add Python 3.13 and fix theme issue

[vkbo]

Summary:

This MR adds Python 3.13 support for the 2.5 branch and fixes an issue with the default light theme. It also fixes a broken link in the docs.

Related Issue(s):

Closes #2042
Closes #2057

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed