feat: implement self-healing online model retraining loop on statistical data drift detection

feat: upgrade fraud detection to XGBoost & SHAP local explanations with premium dashboard

feat: complete NeuralVault 3.0 hardening including AST parameterization fix, KS data drift, Cross-Encoder, and Docker Compose

feat: NeuralVault 2.0 - Complete Free-Tier Groq & ML Explainability Architecture