fix: commit bm25_index.pkl for HF Spaces deployment

debug: print QDRANT_URL

Vietnamese tokenization (underthesea) + query rewriting

hybrid search - Qdrant + BM25 + RRF, switch LLM to Groq

two-tier parsing - pypdf for PDF, EasyOCR for images, structure-aware chunking

Week 1: minimal RAG pipeline - loader, chunker, embedder, vector store, CLI