重构前端 Wave0-2 体验基线（05-28-frontend-ux-redesign）

client/src/layouts/AppShellLayout.tsx

@@ -59,11 +59,11 @@ export function AppShellLayout() {
   }
 
   return (
-    <div className="relative flex min-h-screen overflow-hidden bg-[var(--color-bg-canvas)]">
+    <div className="app-shell relative flex min-h-screen overflow-hidden">
       {isMobileRoute ? null : <Sidebar />}
 
       <main
-        className={`flex min-w-0 flex-1 flex-col ${isMobileRoute ? "hyb-mobile-shell overflow-hidden" : "lg:ml-72"}`}
+        className={`app-shell-main flex min-w-0 flex-1 flex-col ${isMobileRoute ? "hyb-mobile-shell overflow-hidden" : "lg:ml-72"}`}
         style={isMobileRoute ? { height: "var(--mobile-viewport-height, 100vh)", maxHeight: "var(--mobile-viewport-height, 100vh)", minHeight: "var(--mobile-viewport-height, 100vh)" } : undefined}
       >
         {isMobileRoute ? null : <Topbar />}