style: polish SHAP labels and optimize NLP cache retry logic

feat: upgrade NLP engine with deep search, fallbacks, and neutral signal detection

fix: correct depreciation labels, add counter-offer rows, fix NLP 0.00 display, fix ledger table layout

feat: implement professional PDF negotiation reports and terminology refinement

feat: add Dockerfile for HuggingFace Spaces deployment + fix path resolution for Docker

feat: production web app — React/Vite frontend + FastAPI backend with Render/Vercel deployment