Don't reveal the win banner before winner_amount_sats is known (B-50)

winner_user_id is committed as soon as the draw picks a winner, but
winner_amount_sats isn't set until the payout tx is built afterwards
(a real Electrum listunspent round-trip later, in a separate DB
transaction). The frontend revealed the win banner as soon as
winner_user_id appeared, formatPlm(undefined) rendered as "—", and
the toast/result box briefly showed "You won! +— PLM" until the next
poll picked up the real amount. Gate the winner's own reveal on
winner_amount_sats also being non-null; a loss can still reveal
immediately since it never needs the amount.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/static/app.js

@@ -488,11 +488,21 @@ async function refreshRound() {
       // myUserId may not be loaded yet on the very first tick after a reload
       // (refreshMe() and refreshRound() run concurrently) — fall back to the
       // persisted result rather than risk showing nothing or the wrong side.
+      // winner_user_id is committed as soon as the draw picks a winner, but
+      // winner_amount_sats isn't set until the payout tx is built afterwards
+      // (a real Electrum round-trip later) — revealing a win before then would
+      // show "+— PLM". Only the winner's own reveal needs to wait for it.
+      const iWon = myUserId != null && data.winner_user_id === myUserId;
+      const amountReady = !iWon || data.winner_amount_sats != null;
       const canReveal =
-        data.user_played && data.winner_user_id != null && (alreadyKnown || elapsedMs >= minMs) && myUserId != null;
+        data.user_played &&
+        data.winner_user_id != null &&
+        (alreadyKnown || elapsedMs >= minMs) &&
+        myUserId != null &&
+        amountReady;
 
       if (canReveal) {
-        const won = data.winner_user_id === myUserId;
+        const won = iWon;
         if (!alreadyKnown) {
           persistResult(data.round_id, won, data.winner_amount_sats);
           if (won) {