Add scikit-learn dependency for scaler loading

The scaler.bin file was saved using sklearn StandardScaler,
so scikit-learn is required to unpickle it with joblib.

Fixes: ModuleNotFoundError: No module named 'sklearn'

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

requirements.txt

@@ -9,6 +9,7 @@ torch==2.1.0
 torchvision==0.16.0
 numpy==1.26.4
 joblib==1.3.2
+scikit-learn==1.3.2
 
 # Computer Vision & MediaPipe
 opencv-python-headless==4.10.0.84