Add favicon

Link /assets/favicon.ico from every page and serve /favicon.ico without
requiring the access key (browsers request it on their own).

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

public/create.html

@@ -6,6 +6,7 @@
   <meta name="theme-color" content="#24493b">
   <meta name="robots" content="noindex, nofollow">
   <title>テーブル作成 - Hold'em Night</title>
+  <link rel="icon" href="/assets/favicon.ico">
   <link rel="stylesheet" href="/assets/style.css">
 </head>
 <body>

public/key.html

@@ -6,6 +6,7 @@
   <meta name="theme-color" content="#24493b">
   <meta name="robots" content="noindex, nofollow">
   <title>Hold'em Night</title>
+  <link rel="icon" href="/assets/favicon.ico">
   <link rel="stylesheet" href="/assets/style.css">
 </head>
 <body>

public/lobby.html

@@ -6,6 +6,7 @@
   <meta name="theme-color" content="#24493b">
   <meta name="robots" content="noindex, nofollow">
   <title>Hold'em Night</title>
+  <link rel="icon" href="/assets/favicon.ico">
   <link rel="stylesheet" href="/assets/style.css">
 </head>
 <body>

public/table.html

@@ -6,6 +6,7 @@
   <meta name="theme-color" content="#24493b">
   <meta name="robots" content="noindex, nofollow">
   <title>テーブル - Hold'em Night</title>
+  <link rel="icon" href="/assets/favicon.ico">
   <link rel="stylesheet" href="/assets/style.css">
 </head>
 <body class="table-page">

server/index.js

@@ -67,6 +67,7 @@ const tables = new TableManager();
 
 // ---------- 認証不要 ----------
 app.use('/assets', express.static(path.join(PUBLIC, 'assets'), { index: false, dotfiles: 'deny' }));
+app.get('/favicon.ico', (req, res) => res.sendFile(path.join(PUBLIC, 'assets', 'favicon.ico')));
 app.get('/robots.txt', (req, res) => res.type('text/plain').send('User-agent: *\nDisallow: /\n'));
 app.get('/key', (req, res) => {
   if (auth.isAuthed(req)) return res.redirect(auth.safeNext(req.query.next));