Phase 7: add a landing page at GET / for non-technical visitors

Mark Phase 5 and 6 done: live on Hugging Face Spaces

Prepare for Hugging Face Space deployment

Add Phase 3 (FastAPI serving), Phase 4 (LangChain review agent), and Phase 4.5 (RAG chatbot)

Initial commit: Phase 1 (data prep) and Phase 2 (QLoRA fine-tuning) complete