fix: match advanced FEN page height model to the rest of the shell

This page was the only PageSidebarLayout consumer still using
h-screen/max-h-screen with its own data-page-scroll marker, left
over from before the shared layout switched to sizing off its
parent. Since #main-content is already shorter than 100vh (navbar
offset), h-screen made the page taller than its container and
created a second, nested scroll context — which broke the sidebar's
sticky positioning here specifically while every other tab page
(About, Settings, Export, FEN History) stayed fixed correctly.

Switched it to md:h-full/md:max-h-full like the rest so the sidebar
and separator behave the same everywhere.

Author: BilgeGates

src/pages/AdvancedFENInputPage/AdvancedFENInputPage.tsx

@@ -71,10 +71,7 @@ const AdvancedFENInputPage = memo(function AdvancedFENInputPage(
   );
 
   return (
-    <div
-      data-page-scroll
-      className="bg-bg min-h-full md:h-screen md:max-h-screen md:overflow-hidden"
-    >
+    <div className="bg-bg min-h-full md:h-full md:max-h-full">
       <Seo
         {...getRouteSeo('/advanced-fen')}
         schema={[SOFTWARE_APP_SCHEMA, ADVANCED_FEN_BREADCRUMB_SCHEMA]}