Add optional card mode: server deals cards and settles showdowns automatically

- New "カードを配る" switch on the create-table screen (default off); the lobby
  shows "カードあり" for tables that use it
- Card mode (server/cards.js restored): crypto-shuffled deck kept server-side,
  hole cards sent only to their owner until showdown/all-in reveal, board dealt
  per street with burns, all-in runout on a timer (frozen while paused)
- Showdown is evaluated and every pot (incl. side pots, split pots) is paid out
  automatically; host winner selection is only used when card mode is off
- Play UI: board, hole cards, own cards in the action bar, hand names, winning
  cards highlighted; layout tuned for 7+ seats and short screens
- Playing-card styles use .pcard so they don't clash with the existing .card panel
- Tests for hand evaluation, card privacy, runout, side pots, ties and random play

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

public/assets/create.js

@@ -16,6 +16,8 @@
   const timerInput = $('timer');
   const intervalInput = $('interval');
   const scheduleEl = $('schedule');
+  const cardsInput = $('cards');
+  const cardsHint = $('cards-hint');
   const blindHint = $('blind-hint');
   const errorEl = $('error');
   const submitBtn = $('submit');
@@ -66,9 +68,16 @@
       .join('');
   }
 
+  function updateCardsHint() {
+    cardsHint.textContent = cardsInput.checked
+      ? 'オン: 各自のスマホに手札が配られ、勝敗とポットの分配は自動'
+      : 'オフ: 実物のカードで遊び、ショーダウンの勝者はホストが選ぶ';
+  }
+
   function refresh() {
     updateHint();
     updateSchedule();
+    updateCardsHint();
   }
 
   stackInput.addEventListener('input', () => {
@@ -91,6 +100,7 @@
   });
   timerInput.addEventListener('change', refresh);
   intervalInput.addEventListener('input', refresh);
+  cardsInput.addEventListener('change', refresh);
   $('reroll').addEventListener('click', suggestName);
 
   function validate() {
@@ -128,6 +138,7 @@
         bigBlind: int(bbInput),
         blindTimerEnabled: timerInput.checked,
         blindIntervalMin: int(intervalInput),
+        cardsEnabled: cardsInput.checked,
         token: Store.token,
       });
       location.href = '/table/' + encodeURIComponent(id);