Add Dis-Solved BBB predictor and ADMET toolkit

[abinittio]

Adds two open-source tools to the Machine Learning section:

• StereoAwareGNN — stereo-aware GNN for blood-brain barrier permeability prediction with explicit 3D stereochemical encoding (0.96 external AUC, validated on 7,807 compounds).
• Insilico Drug Discovery Toolkit — comprehensive ADMET prediction suite covering monoamine transporter profiling (0.968 AUC), hERG cardiotoxicity (0.91 AUC), CYP450 metabolism (0.88 AUC), and abuse liability scoring.

Both are free, open-source, and deployed as web apps on Streamlit Community Cloud. Built with RDKit, PyTorch Geometric, and DGL.