ci: Fix doc dependency resolving

[ValerianRey]

• uv somehow decides to constrain libraries to be compatible with the whole range of python versions supported by torchjd (3.10-3.13) when resolving, so it does not install libraries that require python 3.11+ for example, even when using python 3.13. This leads to outdated library versions installed in the CI and locally, especially documentation-related libraries.
• Adding --python-version=... forces uv to resolve libraries compatible with the specified python version only, fixing the issue
• When using uv run ..., uv automatically re-syncs. There's no way to specify the python-version for which to resolve when this happens, so the idea is to prevent this resyncing by either using --no-sync everytime we call uv run, or by using the UV_NO_SYNC=1 environment variable. This is done in both ci files that have a uv run, and it's now recommended in CONTRIBUTING.md
• Uncap furo (our sphinx theme): it just changes color of already-clicked links, which is not that bad IMO (and we can probably override this). It's also required for compatibility with more recent versions of other libraries.
• Increase lower cap of sphinx-autodoc-typehints. Before 3.5.0, it's not compatible with Python 3.14.

[codecov]

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[ValerianRey]

@PierreQuinton FYI: you should:

• Add export UV_NO_SYNC=1 in your .zshrc
• Update your installation alias (if you have any) to add --python-version=3.14
• Restart terminal
• Reinstall torchjd
• Call uv run python and check that uv pip show sphinx-autodoc is at version 3.5.2