Add category detail URLs and polish mega menu UX.

Route categories to /products/category/{id}/{slug}, improve menu hover/layout, and hide stock/category clutter on product cards.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/products/[id]/[slug]/page.tsx

@@ -149,9 +149,11 @@ export default async function ProductDetailsPage({
                 )}
               </p>
             </div>
-            <p className={`mt-2 text-[13px] ${inStock ? "text-emerald-600" : "text-brand"}`}>
-              {inStock ? "موجود در فروشگاه" : "ناموجود"}
-            </p>
+            {price != null ? (
+              <p className={`mt-2 text-[13px] ${inStock ? "text-emerald-600" : "text-brand"}`}>
+                {inStock ? "موجود در فروشگاه" : "ناموجود"}
+              </p>
+            ) : null}
 
             {variants.length > 1 ? (
               <div className="mt-5 flex flex-wrap gap-2">