perf: reduce mobile compositing work

app/styles/global.css

@@ -530,7 +530,6 @@ a {
   pointer-events: none;
   filter: blur(110px);
   opacity: 0.12;
-  animation: ambient-float 16s ease-in-out infinite alternate;
 }
 .docs-shell::before {
   top: -16rem;
@@ -541,7 +540,6 @@ a {
   right: -15rem;
   bottom: -18rem;
   background: #a855f7;
-  animation-delay: -7s;
 }
 .topbar {
   position: sticky;
@@ -575,7 +573,6 @@ a {
   color: white;
   background: linear-gradient(145deg, #6366f1, #8b5cf6);
   box-shadow: 0 8px 24px rgba(99, 102, 241, 0.3);
-  animation: logo-pulse 4s ease-in-out infinite;
 }
 .topbar nav {
   display: flex;
@@ -859,7 +856,6 @@ footer nav {
   background-size: 240% auto;
   background-clip: text;
   font-style: normal;
-  animation: gradient-shift 7s linear infinite;
 }
 .hero > p {
   width: min(720px, 100%);
@@ -1375,9 +1371,16 @@ footer a {
 }
 
 @media (max-width: 900px) {
+  .docs-shell::before,
+  .docs-shell::after {
+    display: none;
+  }
+
   .topbar {
     grid-template-columns: 1fr auto;
     padding: 0 20px;
+    background: var(--bg);
+    backdrop-filter: none;
   }
   .topbar nav {
     display: none;