[PyWrapper] Added hybrid PyTorch-SU2 coupling example

[ayush4874]

This PR adds a standalone example demonstrating how to couple SU2 with PyTorch using the Python Wrapper.

Files:

• train_online.py: Driver script for bidirectional coupling.
• inv_NACA0012.cfg: Configuration file.
• mesh_NACA0012_inv.su2: Mesh file.

Context:
Migrated from su2code/SU2#2638 and the tracking issue su2code/SU2#2637 as per discussion with @bigfooted.
This example serves as a reference for users implementing online surrogate modeling or PIML workflows.

[ayush4874]

Hi @bigfooted,

I've successfully migrated the tutorial files here and opened the corresponding documentation PR in the website repo (su2code/su2code.github.io#189).

Regarding the regression test: I am ready to implement this, but I have a technical concern. This tutorial depends on torch, and I noticed that the current regression.yml in the main repo doesn't seem to include PyTorch in the environment.

Should I:

1. Structure the test to be skipped if torch is not found?
2. Or would you prefer to merge this as a "manual-only" tutorial for now to avoid modifying the CI environment?

I’m available to implement whichever path you prefer before the holiday break. Thanks!