Add wishlist feature (frontend), gated by CompanySettings.wishlistEnabled

New: useWishlist.ts (fetch+optimistic-toggle hook, server-backed since
a wishlist needs a logged-in customer, unlike the guest-friendly cart),
WishlistButton.tsx (heart toggle, login-redirects on 401), Navbar's
wishlist icon+badge (hidden below sm: — Account+Cart are the only
always-visible icons on true mobile, a 3rd icon there risks the same
computed nav-overflow class of bug documented in the figma-to-nextjs
skill), and /konto/merkliste (list page, 404s if the feature gets
disabled after a customer already has rows).

Product gained numericId (the raw Payload id) alongside its existing
slug id — WishlistItems.product is a real numeric relationship field,
unlike cart/checkout's slug-keyed "commerce id".

Backend counterpart (WishlistItems collection, CompanySettings toggle,
migration) already deployed separately.

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

app/lib/payload.ts

@@ -173,6 +173,13 @@ export async function getPostBySlug(slug: string, options?: { draft?: boolean })
 // to numeric ids here would silently orphan every existing shopper's cart.
 export type Product = {
   id: string;
+  // The raw Payload numeric id — `id` above is the slug (used everywhere
+  // as the "commerce id" — cart, checkout, URLs), but a few relationships
+  // (Orders.items.product, WishlistItems.product) are real Payload
+  // relationship fields storing this number instead. Kept alongside the
+  // slug rather than replacing it, to avoid touching every existing
+  // slug-based call site.
+  numericId: number;
   name: string;
   description: string;
   price: number;
@@ -290,6 +297,7 @@ function maxPurchasableQty(trackInventory: boolean, stock: number | null, allowB
 export function mapPayloadProduct(product: PayloadProduct): Product {
   return {
     id: product.slug,
+    numericId: product.id,
     name: product.name,
     description: product.description ?? "",
     price: product.price,
@@ -353,6 +361,23 @@ export async function getProductBySlug(slug: string): Promise<Product | null> {
 // from getProducts()'s slug-keyed catalog (an order can reference a
 // product that's since been deactivated/deleted, and slugs aren't even
 // the key an order item stores).
+// Powers /konto/merkliste — WishlistItems.product is a real numeric
+// relationship (see Product.numericId's own comment), so displaying the
+// wishlist needs a numeric-id lookup rather than getProducts()'s
+// slug-keyed list.
+export async function getProductsByIds(ids: number[]): Promise<Product[]> {
+  const uniqueIds = [...new Set(ids)];
+  if (uniqueIds.length === 0) return [];
+  const params = new URLSearchParams({ "where[id][in]": uniqueIds.join(","), depth: "2", limit: String(uniqueIds.length) });
+  const res = await fetch(`${PAYLOAD_URL}/api/products?${params}`, { next: { revalidate: 60 } });
+  if (!res.ok) {
+    console.error(`getProductsByIds: Payload returned ${res.status} ${res.statusText}`);
+    return [];
+  }
+  const data: { docs?: PayloadProduct[] } = await res.json();
+  return (data.docs ?? []).map(mapPayloadProduct);
+}
+
 export async function getProductImagesByIds(ids: number[]): Promise<Map<number, string>> {
   const uniqueIds = [...new Set(ids)];
   const map = new Map<number, string>();
@@ -977,6 +1002,26 @@ export async function getKleinunternehmer(): Promise<boolean> {
   return data.docs?.[0]?.kleinunternehmer ?? false;
 }
 
+// Same ISR-cached, public-catalog-freshness fetch as getKleinunternehmer()
+// above — gates the whole Wishlist feature (heart icon, /konto/merkliste,
+// the Navbar link) site-wide. Deliberately off by default (see
+// CompanySettings.ts's own field comment) so the feature stays entirely
+// invisible in the frontend until a tenant actually wants it, rather than
+// shipping a half-finished-looking icon everywhere.
+export async function getWishlistEnabled(): Promise<boolean> {
+  const params = new URLSearchParams({ "where[tenant.slug][equals]": TENANT_SLUG, limit: "1" });
+  const res = await fetch(`${PAYLOAD_URL}/api/company-settings?${params}`, {
+    headers: { "x-order-service-secret": process.env.ORDER_SERVICE_SECRET || "" },
+    next: { revalidate: 60 },
+  });
+  if (!res.ok) {
+    console.error(`getWishlistEnabled: Payload returned ${res.status} ${res.statusText}`);
+    return false;
+  }
+  const data: { docs?: { wishlistEnabled?: boolean }[] } = await res.json();
+  return data.docs?.[0]?.wishlistEnabled ?? false;
+}
+
 export type SeoSettings = {
   defaultTitle: string | null;
   titleTemplate: string | null;