optimize mobile page

- the animated background caused performance issues
- use lvw/lvh on background to make it fill the entire viewport

index.css

@@ -17,14 +17,15 @@ html {
 html::before {
     content: '';
     position: absolute;
-    inset: 0;
+    top: 0;
+    left: 0;
+    width: 100lvw;
+    height: 100lvh;
     z-index: -1;
 
-    --gradient-angle: 0deg;
-    background: conic-gradient(from var(--gradient-angle) in hsl longer hue, hsl(0deg 100% 12.5%) 0 0);
+    background: conic-gradient(from 0deg in hsl longer hue, hsl(0deg 100% 12.5%) 0 0);
     mask-image: url("pattern.svg");
     mask-size: 5rem;
-    animation: rotation 300s infinite linear;
 }
 
 body {