fix: replace Google embeddings with HuggingFace sentence-transformers (no API key needed)

fix: pin langchain-google-genai<2.0 to restore working embedding-001 model

fix: update Google embedding model from embedding-001 to text-embedding-004

fix: replace deprecated langchain.text_splitter with langchain-text-splitters

fix: lazy Pinecone init so FastAPI starts cleanly on HF Spaces

feat: production deployment setup for HF Spaces