Add a settings page for profit display and default stack

- Per-device toggle to hide your own net and the net ranking at tables
- Default starting stack set in settings; creating a table saves the
  stack, SB and BB used as the next defaults
- Number fields on create and settings select all on focus

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

public/settings.html

@@ -0,0 +1,54 @@
+<!doctype html>
+<html lang="ja">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no, viewport-fit=cover">
+  <meta name="theme-color" media="(prefers-color-scheme: light)" content="#f2f2f7">
+  <meta name="theme-color" media="(prefers-color-scheme: dark)" content="#000000">
+  <meta name="robots" content="noindex, nofollow">
+  <title>設定 - Hold'em Night</title>
+  <link rel="icon" href="/assets/favicon.ico">
+  <link rel="stylesheet" href="/assets/style.css">
+</head>
+<body class="page-settings">
+  <header class="nav-bar" id="nav">
+    <div class="nav-inner">
+      <a class="nav-back" href="/"><svg class="i" viewBox="0 0 24 24" aria-hidden="true"><path d="M15 5l-7 7 7 7"/></svg>ロビー</a>
+      <span class="nav-title"></span>
+    </div>
+  </header>
+
+  <main class="wrap">
+    <h1 class="large-title" id="large-title">設定</h1>
+
+    <section class="group">
+      <div class="group-header">テーブル</div>
+      <div class="list">
+        <div class="cell">
+          <span class="cell-title" id="show-net-label">収支を表示</span>
+          <span class="switch">
+            <input id="show-net" type="checkbox" aria-labelledby="show-net-label">
+            <span></span>
+          </span>
+        </div>
+      </div>
+      <div class="group-footer">オフにすると、テーブルで自分の収支と、ランキングの「収支」が表示されなくなります。この端末だけの設定で、他の人の画面は変わりません。</div>
+    </section>
+
+    <section class="group">
+      <div class="group-header">テーブルの作成</div>
+      <div class="list">
+        <div class="cell field-cell value-right">
+          <label for="default-stack">開始スタック</label>
+          <input id="default-stack" type="number" inputmode="numeric" min="10" step="1">
+        </div>
+      </div>
+      <div class="group-footer" id="stack-hint">テーブルを作るときの初期値です。テーブルを作ると、そのときの値（SB・BB も）が次回の初期値になります。</div>
+    </section>
+  </main>
+
+  <script src="/assets/fluid.js"></script>
+  <script src="/assets/common.js"></script>
+  <script src="/assets/settings.js"></script>
+</body>
+</html>