chore: codebase audit and fixes (ruff, mypy, pytest)

Fix codebase issues: linting, types, tests, and security.

fix: all 15 bugs + full agentic RAG pipeline in HF Space

Fix HF bugs: HTML rendering, Q&A validation, add separate Q&A tab

Production Upgrade v2.0: SSE streaming, HIPAA compliance, Gradio Q&A UI

feat: Enable 100% HF Space capability with dynamic environment variables

Fix: Improve UI formatting and handle missing biomarker data gracefully

Overhaul Gradio UI with modern medical design

Fix: Dynamic API key loading - secrets now work properly on HuggingFace Spaces

Fix HF deployment: add langchain-text-splitters, langchain-huggingface, simplify env

Deploy to HuggingFace Spaces - Medical RAG with vector store