Add FRED API key validation at app startup and improve environment variable loading

Fix streamlit_app.py to properly use imported main() function instead of always overriding with fallback

Fix Streamlit Cloud deployment import issue - Added robust import handling with fallbacks - Added current directory to Python path - Added error handling for import failures - Improved debugging output for deployment troubleshooting

Optimize Streamlit app performance with lazy imports and loading indicators

Fix Streamlit Cloud deployment issues and deprecated pandas warnings

Prepare for Streamlit Cloud deployment - Add deployment files, fix clustering chart error, update requirements