fix: bump CSS cache-busting version to force reload

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lan-client/index.html

@@ -4,7 +4,7 @@
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>MTG Commander Battlefield</title>
-<link rel="stylesheet" href="style.css?v=20260403_0300">
+<link rel="stylesheet" href="style.css?v=20260404_0100">
 </head>
 <body>