Refactor layout components to improve responsiveness and accessibility; integrate appShell classes for consistent styling across DesktopAIShell and BottomNav. Update SelectPage to enhance option selection UI with image support and language filtering logic in SystemPage for better localization handling.

client/src/App.tsx

@@ -22,6 +22,7 @@ import AIPage from "./pages/AIPage";
 import CommunityPage from "./pages/CommunityPage";
 import { AIDrawerProvider } from "./contexts/AIDrawerContext";
 import DesktopAIShell from "./components/DesktopAIShell";
+import { appShellColumnClass, appShellGutterClass } from "./lib/appShell";
 
 function AIPageRoute() {
   return <AIPage />;
@@ -59,9 +60,10 @@ function App() {
             <Toaster />
             <Router hook={useHashLocation}>
               <AIDrawerProvider>
-                {/* Desktop: narrow shell centered in the browser with side gutters */}
-                <div className="min-h-dvh bg-[#0d1117]">
-                  <div className="mx-auto min-h-dvh w-full max-w-full lg:max-w-[min(1180px,calc(100vw-3rem))]">
+                <div
+                  className={`min-h-dvh bg-[#0d1117] flex justify-center ${appShellGutterClass}`}
+                >
+                  <div className={`min-h-dvh ${appShellColumnClass}`}>
                     <DesktopAIShell>
                       <AppRouter />
                     </DesktopAIShell>