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/table.html

@@ -38,6 +38,7 @@
       <div class="felt">
         <div class="pot-label">POT</div>
         <div class="pot" id="pot">$0</div>
+        <div class="board" id="board" hidden></div>
         <div class="phase"><span id="phase">WAITING</span><span class="hand-no" id="hand-no"></span></div>
         <div class="result" id="result" hidden></div>
       </div>
@@ -53,9 +54,10 @@
   <div class="action-bar" id="action-bar" hidden>
     <div class="inner">
       <div class="me-row">
+        <div class="my-cards" id="my-cards" hidden></div>
         <div class="me-info">
           <div class="my-stack"><span class="wallet">👛</span><span id="my-stack">$0</span></div>
-          <div class="me-sub"><span id="my-net"></span><span class="my-bet" id="my-bet"></span></div>
+          <div class="me-sub"><span class="my-hand" id="my-hand"></span><span id="my-net"></span><span class="my-bet" id="my-bet"></span></div>
         </div>
         <button class="btn btn-ghost btn-sm" id="sit-out" title="次のハンドから参加しません">離席</button>
       </div>