ticker-serve style: add a gradient background

ticker-serve/static/style.css

@@ -2,7 +2,8 @@ body {
     font-family: sans-serif;
     margin: 0 auto;
     padding: 1rem 0 0 1.5rem;
-    background-color: #373737;
+    background: #374757;
+    background: linear-gradient(135deg, #270000 0%, #001000 20%, #172737 100%) fixed;
     color: #e7e7e7;
     max-width: 40rem;
 }