Create repository skeleton, .gitignore and requirements.txt

Basic project layout every other issue builds on.

Files: src/__init__.py, .gitignore, requirements.txt, README.md

Tasks

• Create folders src/, scripts/, tests/, notebooks/, results/, figures/, data/ (add .gitkeep where empty)
• .gitignore: data/, *.pt, *.pth, *.npz, __pycache__/, .ipynb_checkpoints/
• requirements.txt: torch, torchvision, timm, thop, scikit-learn, numpy, matplotlib, pillow, datasets, pytest
• README: project title, dataset link, folder layout

Done when

pip install -r requirements.txt works on a fresh environment.

Close with a commit or PR message containing Closes #<this issue>.