Update README

Update README with QALoop architecture diagram via GitHub URL

Update README and license

Update HF demo seed and document demo.sql workflow.

Add default LLM settings with LLM_API_KEY from environment

Fix FastAPI deprecation warnings and lengthen demo SECRET_KEY

Pre-fill demo admin credentials on login page

Add demo defaults and usage instructions for HF Space

Default admin password to 123456 for HF Space

Add Hugging Face Space deployment