feat: add Python 3.13 support

[zfried]

Summary

Thanks for this great tool! This PR adds Python 3.13 support by:

• Updating requires-python from >=3.10,<3.13 to >=3.10,<3.14
• Adding Python 3.13 to the CI install and test matrices
• Updating the README badge and contributor documentation

Validation

The test suite passes locally on Python 3.13:

• 21 tests passed
• 7 tests skipped because the optional cached CCD asset was unavailable locally
• Ruff linting and formatting checks passed

GPU inference was compared using the exact code from this feature branch under Python 3.13 and the exact code from the current repository under Python 3.12. Both environments used NVIDIA L4 GPUs with matching model files, dependencies, CUDA/PyTorch versions, inputs, seeds, precision, and inference settings.

The Python 3.13 results showed extremely high agreement with the Python 3.12 results across all three tested input formats: sequence+SDF, sequence+SMILES, and sequence+CCD.

These results seem to indicate that Nesso's installation and tested GPU inference paths work correctly on Python 3.13.

[shenoynikhil]

Thanks for testing this out @zfried and contributing to this repo!