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>

lib/store.ts

@@ -255,7 +255,7 @@ export function catalogProductToCard(product: CatalogProduct): Product {
     id: String(product.id),
     href: productHref(product),
     title: catalogTitle(product),
-    brand: brandName(product) || product.categoryNameFa || "",
+    brand: brandName(product),
     price: price ?? undefined,
     image: product.thumbnailUrl || product.image || product.thumbnail || PLACEHOLDER,
     inStock: product.store?.inStock !== false,