Fix product links, equalize card heights, and switch to IRANYekan

- Resolve product cards from group endpoints (store-specials,
  brand-groups) that only return a productId, not a slug, via a new
  /products/id/[id] route backed by GET /products/by-id/{id} — clicking
  these was previously falling back to a name search instead of the
  detail page.
- Derive discount price/percent generically in normalizeProduct so any
  source with real old/new prices shows it, even without an explicit
  discount field from the API.
- Product cards and the detail page buy-box: show the discount badge
  beside the old (struck-through) price, current price alone on its
  own line, matching the reference design.
- Equalize product card heights within a carousel row (Swiper's own
  CSS doesn't stretch slides to the tallest sibling in slidesPerView:
  "auto" + freeMode mode) so the add-to-cart button lines up across
  cards regardless of whether a card has a discount line.
- Featured categories: 110px images with no border/radius, matching
  the site's other category card treatment.
- Replace Vazirmatn with the client's IRANYekan font files — light
  weight for body text, bold weight for headings only.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/components/ui/Carousel.tsx

@@ -79,7 +79,11 @@ export function Carousel({ children, ariaLabel }: CarouselProps) {
         className="!px-1 !py-2"
       >
         {Children.map(children, (child) => (
-          <SwiperSlide style={{ width: "auto" }}>{child}</SwiperSlide>
+          // Swiper's own CSS pins slide height to 100%, which — with no definite
+          // wrapper height — resolves per-slide instead of stretching to match
+          // the tallest sibling. height:auto (inline, so it wins) lets normal
+          // flex stretch equalize card heights across a row.
+          <SwiperSlide style={{ width: "auto", height: "auto" }}>{child}</SwiperSlide>
         ))}
       </Swiper>
     </div>