Update site selection logic in app.py: move 'Select Site' dropdown above 'Clear data' button and adjust minimum lineup edge input precision.

Refactor portfolio loading logic in app.py: ensure portfolio is only loaded if not already in session state, and add minimum lineup edge input for filtering.

Refactor Streamlit UI in app.py: reorganize layout for clearer user interaction and restore 'Clear data' button functionality.

Add initial Streamlit application with data loading, portfolio management, and optimization features