Replace native confirm() with an in-site confirmation dialog

Add App.confirm() in common.js: a promise-based dialog styled like the
site's modals, with a title, multi-line message and custom button labels.
Destructive actions use a red OK button and focus Cancel by default;
Escape and backdrop clicks cancel, and Tab stays inside the dialog.

Use it for folding when a check is possible, leaving the table,
confirming showdown winners and deleting tables from the lobby. After the
dialog closes, re-check that the action is still valid (turn not passed,
pot not already awarded, table still listed) before sending it.

Also add a "poker-test" launch config that runs on port 4672 with the
example keys from .env.example, for local browser testing.

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

public/assets/table.js

@@ -532,7 +532,7 @@
     renderAwardPanel(state.hand.pots);
   });
 
-  $('award-confirm').addEventListener('click', () => {
+  $('award-confirm').addEventListener('click', async () => {
     if (pending || !awardSel.every((set) => set.size > 0)) return;
     const winners = awardSel.map((set) => [...set]);
     const names = winners.map((w) => w.map(nameOf).join('・'));
@@ -540,7 +540,9 @@
       names.length === 1
         ? `${names[0]} の勝ちで確定しますか？`
         : names.map((n, i) => `${i === 0 ? 'メイン' : 'サイド'}: ${n}`).join('\n') + '\nで確定しますか？';
-    if (!confirm(msg)) return;
+    const ok = await App.confirm({ title: '勝者の確定', message: msg, ok: '確定する' });
+    // 確認中に他の人が確定した・ハンドが終わった場合は送らない
+    if (!ok || pending || $('award-panel').hidden) return;
     pending = true;
     emit('table:award', { winners });
     render();
@@ -589,10 +591,20 @@
 
   const options = () => (state && state.me && state.me.options) || null;
 
-  $('act-fold').addEventListener('click', () => {
+  $('act-fold').addEventListener('click', async () => {
     const o = options();
     if (!o) return;
-    if (o.canCheck && !confirm('チェックできます。フォールドしますか？')) return;
+    if (o.canCheck) {
+      const ok = await App.confirm({
+        title: 'フォールドしますか？',
+        message: 'いまはチップを出さずにチェックできます。',
+        ok: 'フォールド',
+        cancel: 'やめる',
+        danger: true,
+      });
+      // 確認中に手番が過ぎていたら何もしない
+      if (!ok || !options()) return;
+    }
     sendAction('fold');
   });
   $('act-call').addEventListener('click', () => {
@@ -672,14 +684,15 @@
   $('rebuy').addEventListener('click', () => emit('table:rebuy'));
   $('take-seat').addEventListener('click', () => join(true));
 
-  $('leave').addEventListener('click', () => {
+  $('leave').addEventListener('click', async () => {
     const me = state && state.mySeat >= 0 ? state.seats[state.mySeat] : null;
     if (!me) return (location.href = '/');
     const inHand = state.hand && !state.hand.finished && me.inHand && !me.folded;
     const msg = inHand
-      ? 'ハンドの途中です。退席するとフォールドになり、チップは失われます。退席しますか？'
-      : 'テーブルから退席しますか？（チップは失われます）';
-    if (!confirm(msg)) return;
+      ? 'ハンドの途中です。退席するとフォールドになり、チップは失われます。'
+      : '退席するとチップは失われます。';
+    const ok = await App.confirm({ title: 'テーブルから退席しますか？', message: msg, ok: '退席する', danger: true });
+    if (!ok) return;
     socket.emit('table:leave', null, () => { location.href = '/'; });
   });