Add portfolio download functionality in app.py: store a copy of the sorted portfolio for download, improving user access to portfolio data after updates.

app.py

@@ -844,6 +844,7 @@ with tab3:
                         
                         st.session_state['portfolio'] = trim_portfolio(st.session_state['portfolio'], performance_type, own_type)
                         st.session_state['portfolio'] = st.session_state['portfolio'].sort_values(by='median', ascending=False)
+                        st.session_state['download_portfolio'] = st.session_state['portfolio'].copy()
 
         with col2:
             st.session_state['portfolio'] = predict_dupes(st.session_state['portfolio'], map_dict, site_var, type_var, Contest_Size, strength_var)