Add support for Python 3.14 in October 2025

[namurphy]

Python 3.14 will be released in October 2025, and we should add it to our test suite and fix any new errors that arise. We'll need to update this in:

Tasks

• Update pyproject.toml
• Update noxfile.py
• Add a changelog entry
• Update the documentation builds to use Python 3.14 on both noxfile.py and on Read the Docs ← we may need to wait a few months to do this, but it's important that we keep documentation builds as consistent as possible across platforms.