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>

server/config.js

@@ -61,8 +61,11 @@ module.exports = {
   // 誰も接続していないテーブルを削除するまでの時間
   EMPTY_TABLE_TTL_MS: 30 * 60 * 1000,
 
-  // ハンド終了後、次のハンドまで結果を表示する時間
+  // オールインで残りの場札をめくる間隔（カード機能あり）
+  RUNOUT_STEP_MS: 1500,
+  // ハンド終了後、次のハンドまで結果を表示する時間（カードありは手札を見比べられるよう長め）
   SHOWDOWN_MS: 4000,
+  CARD_SHOWDOWN_MS: 6000,
   FOLD_WIN_MS: 2500,
   // 参加者が2人揃ってから次のハンドを始めるまで
   NEXT_HAND_DELAY_MS: 2000,