fix: BM25 case-insensitive + add price to drug prefix

fix: remove recursive self.initialize() causing infinite loop

fix: syntax error in initialize() - corrupted text

fix: drug-aware chunking, streaming cleanup, conditional refs

Perf: add SSE streaming, disable Gemini thinking, skip query rewrite when no history

Upgrade Deep mode: 5-step clinical reasoning (guidelines -> pharmacovigilance -> drug matching -> treatment plan); expand auto-detect keywords

Update: NVIDIA fallback to Llama-3.3-70B, skip drug folder in RAG, use consolidated drug reference

fix: include NVIDIA_API_KEY in bot initialization check

Thiết lập lại thư viện y khoa sạch và cập nhật chroma_db