show selling costs transparently in tooltip and label on result card

ui.js

@@ -193,6 +193,7 @@ const build_table = (result) => {
     td_buy_nw.classList.add('has-tip');
     td_buy_nw.addEventListener('mouseenter', (e) => show_tooltip(e, [
       tip_row('Immobilienwert', d.house_value, '#f59e0b'),
+      tip_row('Verkaufskosten', -d.selling_costs, '#ef4444'),
       tip_row('ETF-Portfolio',  d.buyer_portfolio, '#f59e0b'),
       tip_row('Restschuld',    -d.mortgage_balance, '#ef4444'),
     ].join('<br>')));