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>

server/index.js

@@ -92,6 +92,7 @@ app.get('/', page('lobby.html'));
 app.get('/create', page('create.html'));
 app.get('/table/:id', page('table.html'));
 app.get('/stats', page('stats.html'));
+app.get('/settings', page('settings.html'));
 
 // ---------- 管理者専用: ハンドレンジ学習 ----------
 app.get('/range', auth.requireAdmin, page('range.html', ADMIN));