Use DM Sans as the base UI font

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

server/src/wled_controller/templates/index.html

@@ -7,7 +7,7 @@
     <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'><text y='0.9em' font-size='90'>💡</text></svg>">
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
-    <link href="https://fonts.googleapis.com/css2?family=Orbitron:wght@700&display=swap" rel="stylesheet">
+    <link href="https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700&family=Orbitron:wght@700&display=swap" rel="stylesheet">
     <!-- PWA -->
     <meta name="theme-color" content="#1a1a1a">
     <meta name="apple-mobile-web-app-capable" content="yes">