* feat(rag): Phase 2 — ChromaDB vector index over bulk card DB * feat(rag): add routes/rag.py with build, search, status endpoints * Update lab_api.pyfeat(rag): register rag_router in lab_api.py, remove old inline rag_status * Update requirements.txtfeat(rag): add chromadb>=0.5.0 to requirements.txtfeat(rag): add chromadb to requirements.txt