[Docs] Added Hybrid PyTorch-SU2 Coupling Page

[ayush4874]

Adds a documentation page (_tutorials/workflow_features/hybrid_ml_coupling.md) for the new PyTorch coupling example.

Context:

• This page documents the usage of the script submitted in [PyWrapper] Added hybrid PyTorch-SU2 coupling example Tutorials#71.
• Provides a high-level overview of the CSinglezoneDriver loop for online training.
• Relates to Docs: Added PyTorch-SU2 coupling example to Python wrapper SU2#2638 and the tracking issue [Docs] Missing examples for direct Python-ML coupling (PyTorch/TensorFlow) SU2#2637.

[bigfooted]

You can test if the page looks good in-situ on your own machine using:
bundle exec jekyll serve
Just run it from the su2code.github.io github branch on your local machine...

[ayush4874]

Thanks @bigfooted, I appreciate the tip! I'll spin up the local Jekyll server and verify the layout/rendering to make sure everything looks correct before the final review.

[ayush4874]

@bigfooted Ready for review.

Summary of Changes

1. Added Tutorial: "Hybrid PyTorch-SU2 Coupling" via Python Wrapper.
2. Verified Code: Ran the simulation locally with mpirun -n 4.
   • Physics solver converges (Density residuals dropped to ~10^-11).
   • ML model learns in real-time (MSE Loss dropped from ~70 to ~0.16).
3. Verified Rendering: Built the site locally using bundle exec jekyll serve and confirmed the tutorial page renders correctly with the correct links.