fix: stabilize SidebarMenuSkeleton random width across re-renders

Use useState initializer instead of plain expression for Math.random()
to ensure the skeleton width remains stable for the component lifetime.
The React Compiler does not memoize impure functions like Math.random(),
causing visible flickering on re-renders.

Author: cursoragent

apps/web/src/components/ui/sidebar.tsx

@@ -889,8 +889,8 @@ function SidebarMenuSkeleton({
 }: React.ComponentProps<"div"> & {
   showIcon?: boolean;
 }) {
-  // Random width between 50 to 90%.
-  const width = `${Math.floor(Math.random() * 40) + 50}%`;
+  // Random width between 50 to 90%, stable across re-renders.
+  const [width] = React.useState(() => `${Math.floor(Math.random() * 40) + 50}%`);
 
   return (
     <div