Fix wishlist heart invisible on mobile product grids

revealOnHover relied purely on group-hover/group-focus-within, both mouse/keyboard-only pseudo-classes with no reliable touch equivalent — a tap on a card never reliably triggers group-hover the way a mouse hover does, leaving the heart permanently hidden on touch devices. Adds pointer-coarse:opacity-100 so it's always visible there; desktop hover-reveal behavior is unchanged.

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

app/components/WishlistButton.tsx

@@ -25,12 +25,11 @@ export function WishlistButton({
    * card is hovered/focused, unless the product is already wishlisted (a
    * filled heart stays as a permanent status indicator) — right for a
    * multi-card grid (ProductGrid.tsx), where a heart on every single card
-   * reads as visual noise (Marco: "sieht man überall Herzen", 2026-07-31).
-   * Relies on the parent card already carrying `group`/`focus-within`
-   * (see ProductGrid.tsx) — Tailwind's plain `:hover`, so tapping a card
-   * on touch devices reveals it the same way the existing
-   * `group-hover:-translate-y-1` card-lift already does, no separate
-   * touch handling needed. */
+   * reads as visual noise. Relies on the parent card already carrying
+   * `group`/`focus-within` (see ProductGrid.tsx). Always visible on
+   * coarse-pointer (touch) devices regardless of hover/focus state —
+   * touch has no persistent `:hover`, so a tap on the card never reliably
+   * reveals a `group-hover`-gated element the way a mouse hover does. */
   revealOnHover?: boolean;
 }) {
   const { isWishlisted, toggle } = useWishlist();
@@ -63,7 +62,7 @@ export function WishlistButton({
       disabled={pending}
       className={`flex h-9 w-9 items-center justify-center rounded-full bg-bg-base/90 backdrop-blur-sm transition-all active:scale-90 disabled:opacity-60 ${
         revealOnHover && !wishlisted
-          ? "opacity-0 group-hover:opacity-100 group-focus-within:opacity-100 focus-visible:opacity-100"
+          ? "opacity-0 group-hover:opacity-100 group-focus-within:opacity-100 focus-visible:opacity-100 pointer-coarse:opacity-100"
           : ""
       } ${className}`}
     >