metatrain: add v2025.12 and update dependencies

[RMeli]

https://github.com/metatensor/metatrain/releases/tag/v2025.12

[RMeli]

@spackbot fix style

[spackbot-app]

Let me see if I can fix that for you!

[spackbot-app]

I was able to run spack style --fix for you!

spack style --fix

repos/spack_repo/builtin/packages/intel_oneapi_compilers_classic/package.py
repos/spack_repo/builtin/packages/nccl_tests/package.py
repos/spack_repo/builtin/packages/onnx/package.py
repos/spack_repo/builtin/packages/py_metatensor_learn/package.py
repos/spack_repo/builtin/packages/py_metatensor_operations/package.py
repos/spack_repo/builtin/packages/py_metatensor_torch/package.py
repos/spack_repo/builtin/packages/py_metatomic_torch/package.py
repos/spack_repo/builtin/packages/py_metatrain/package.py
repos/spack_repo/builtin/packages/py_onnx/package.py
repos/spack_repo/builtin/packages/py_pydantic/package.py
repos/spack_repo/builtin/packages/py_pydantic_core/package.py
repos/spack_repo/builtin/packages/py_rasterio/package.py
repos/spack_repo/builtin/packages/py_tensorflow/package.py
repos/spack_repo/builtin/packages/py_typing_inspection/package.py
repos/spack_repo/builtin/packages/py_vesin/package.py
�[1;34m==> �[0mrunning flake8
repos/spack_repo/builtin/packages/py_metatensor_torch/package.py:45: [E261] at least two spaces before inline comment
�[1;34m==> �[0mrunning isort
�[1;34m==> �[0mrunning black

Keep in mind that I cannot fix your flake8 or mypy errors, so if you have any you'll need to fix them and update the pull request. If I was able to push to your branch, if you make further changes you will need to pull from your updated branch before pushing again.

I've updated the branch with style fixes.

[Luthaf]

The changes looks good to me!