Fix RSC build break: keep next/headers out of lib/payload.ts

payload.ts's mapping functions/types are also imported by "use client"
components (LiveTestimonialsGrid, LivePostContent) — importing
next/headers anywhere in that module made it unbundlable for the client,
breaking the production build. draftMode() is now only ever called in the
Server Component pages themselves; they pass the resulting boolean into
getPostBySlug/getLegalPage/getTestimonials as a plain `draft` option.

app/agb/page.tsx

@@ -17,9 +17,9 @@ export const metadata: Metadata = {
 };
 
 export default async function AgbPage() {
-  const page = await getLegalPage("agb");
-  const headings = page ? extractHeadings(page.content) : [];
   const { isEnabled: isPreview } = await draftMode();
+  const page = await getLegalPage("agb", { draft: isPreview });
+  const headings = page ? extractHeadings(page.content) : [];
 
   return (
     <>

app/blog/[slug]/page.tsx

@@ -39,7 +39,8 @@ export default async function BlogDetailPage({
   params: Promise<{ slug: string }>;
 }) {
   const { slug } = await params;
-  const post = await getPostBySlug(slug);
+  const { isEnabled: isPreview } = await draftMode();
+  const post = await getPostBySlug(slug, { draft: isPreview });
   if (!post) notFound();
 
   // "Weiterlesen" — any other post, most recent first. Not the current
@@ -47,7 +48,6 @@ export default async function BlogDetailPage({
   // showing a fake/duplicate card when this is the only post.
   const otherPosts = await getBlogPosts(4);
   const nextPost = otherPosts.find((p) => p.slug !== post.slug) ?? null;
-  const { isEnabled: isPreview } = await draftMode();
 
   return (
     <>

app/challenge/page.tsx

@@ -169,8 +169,8 @@ function EmailCapture({ buttonLabel = "Challenge starten" }: { buttonLabel?: str
 }
 
 export default async function ChallengePage() {
-  const testimonials = await getTestimonials("challenge");
   const { isEnabled: isPreview } = await draftMode();
+  const testimonials = await getTestimonials("challenge", { draft: isPreview });
 
   return (
     <>

app/datenschutz/page.tsx

@@ -16,9 +16,9 @@ export const metadata: Metadata = {
 };
 
 export default async function DatenschutzPage() {
-  const page = await getLegalPage("datenschutz");
-  const headings = page ? extractHeadings(page.content) : [];
   const { isEnabled: isPreview } = await draftMode();
+  const page = await getLegalPage("datenschutz", { draft: isPreview });
+  const headings = page ? extractHeadings(page.content) : [];
 
   return (
     <>

app/impressum/page.tsx

@@ -16,9 +16,9 @@ export const metadata: Metadata = {
 };
 
 export default async function ImpressumPage() {
-  const page = await getLegalPage("impressum");
-  const headings = page ? extractHeadings(page.content) : [];
   const { isEnabled: isPreview } = await draftMode();
+  const page = await getLegalPage("impressum", { draft: isPreview });
+  const headings = page ? extractHeadings(page.content) : [];
 
   return (
     <>

app/lib/payload.ts

@@ -1,16 +1,20 @@
-import { draftMode } from "next/headers";
 import { formatPrice } from "./format";
 
 const PAYLOAD_URL = process.env.PAYLOAD_URL || "https://payload.mk360.de";
 const TENANT_SLUG = "einfach-produktiv";
 
 // Used only by the fetchers backing Live Preview (posts, legal pages,
-// testimonials) — Draft Mode is enabled exclusively while a document is
-// open in the Payload admin's Live Preview iframe, so bypassing the normal
-// 60s ISR cache there doesn't affect ordinary site visitors at all.
-async function livePreviewCacheOption(): Promise<{ cache: "no-store" } | { next: { revalidate: 60 } }> {
-  const { isEnabled } = await draftMode();
-  return isEnabled ? { cache: "no-store" } : { next: { revalidate: 60 } };
+// testimonials) — callers pass `draft: true` only while Draft Mode is
+// enabled (a document open in the Payload admin's Live Preview iframe),
+// bypassing the normal 60s ISR cache there without affecting ordinary
+// visitors. Deliberately does NOT call next/headers' draftMode() itself
+// here — this module's mapping functions/types (mapPayloadTestimonial,
+// mapPayloadPost, etc.) are also imported by "use client" components
+// (LiveTestimonialsGrid.tsx, LivePostContent.tsx), and next/headers is a
+// server-only import that breaks the client bundle the moment anything
+// in this file touches it, even indirectly.
+function livePreviewCacheOption(draft: boolean): { cache: "no-store" } | { next: { revalidate: 60 } } {
+  return draft ? { cache: "no-store" } : { next: { revalidate: 60 } };
 }
 
 export type BlogPost = {
@@ -119,7 +123,7 @@ export function mapPayloadPost(doc: PayloadPostDetail): PostDetail {
   };
 }
 
-export async function getPostBySlug(slug: string): Promise<PostDetail | null> {
+export async function getPostBySlug(slug: string, options?: { draft?: boolean }): Promise<PostDetail | null> {
   const params = new URLSearchParams({
     "where[tenant.slug][equals]": TENANT_SLUG,
     "where[slug][equals]": slug,
@@ -127,7 +131,7 @@ export async function getPostBySlug(slug: string): Promise<PostDetail | null> {
     limit: "1",
   });
 
-  const res = await fetch(`${PAYLOAD_URL}/api/posts?${params}`, await livePreviewCacheOption());
+  const res = await fetch(`${PAYLOAD_URL}/api/posts?${params}`, livePreviewCacheOption(Boolean(options?.draft)));
   if (!res.ok) {
     console.error(`getPostBySlug: Payload returned ${res.status} ${res.statusText}`);
     return null;
@@ -538,7 +542,7 @@ export function mapPayloadTestimonial(doc: PayloadTestimonial): Testimonial {
 // hardcoded arrays kept manually in sync. The single-quote "photo band"
 // testimonials on /not-found and /bestellbestaetigung are a different
 // shape (no avatar/role) and are not part of this collection.
-export async function getTestimonials(page: TestimonialsPage): Promise<Testimonial[]> {
+export async function getTestimonials(page: TestimonialsPage, options?: { draft?: boolean }): Promise<Testimonial[]> {
   const params = new URLSearchParams({
     "where[tenant.slug][equals]": TENANT_SLUG,
     "where[page][equals]": page,
@@ -547,7 +551,7 @@ export async function getTestimonials(page: TestimonialsPage): Promise<Testimoni
     limit: "20",
   });
 
-  const res = await fetch(`${PAYLOAD_URL}/api/testimonials?${params}`, await livePreviewCacheOption());
+  const res = await fetch(`${PAYLOAD_URL}/api/testimonials?${params}`, livePreviewCacheOption(Boolean(options?.draft)));
   if (!res.ok) {
     console.error(`getTestimonials: Payload returned ${res.status} ${res.statusText}`);
     return [];
@@ -574,7 +578,7 @@ type PayloadLegalPage = {
   attachment: { url: string; title: string } | number | null;
 };
 
-export async function getLegalPage(type: LegalPageType): Promise<LegalPage | null> {
+export async function getLegalPage(type: LegalPageType, options?: { draft?: boolean }): Promise<LegalPage | null> {
   const params = new URLSearchParams({
     "where[tenant.slug][equals]": TENANT_SLUG,
     "where[type][equals]": type,
@@ -582,7 +586,7 @@ export async function getLegalPage(type: LegalPageType): Promise<LegalPage | nul
     limit: "1",
   });
 
-  const res = await fetch(`${PAYLOAD_URL}/api/legal-pages?${params}`, await livePreviewCacheOption());
+  const res = await fetch(`${PAYLOAD_URL}/api/legal-pages?${params}`, livePreviewCacheOption(Boolean(options?.draft)));
   if (!res.ok) {
     console.error(`getLegalPage: Payload returned ${res.status} ${res.statusText}`);
     return null;

app/newsletter/page.tsx

@@ -39,8 +39,8 @@ export const metadata: Metadata = {
 // weekly newsletter), so this page resolves both at once instead of
 // picking a new URL and leaving one of them still dangling.
 export default async function NewsletterPage() {
-  const testimonials = await getTestimonials("newsletter");
   const { isEnabled: isPreview } = await draftMode();
+  const testimonials = await getTestimonials("newsletter", { draft: isPreview });
 
   return (
     <>

app/todo-cards/page.tsx

@@ -33,8 +33,8 @@ export const metadata: Metadata = {
 };
 
 export default async function TodoCardsPage() {
-  const testimonials = await getTestimonials("todo-cards");
   const { isEnabled: isPreview } = await draftMode();
+  const testimonials = await getTestimonials("todo-cards", { draft: isPreview });
 
   return (
     <>

app/widerruf/page.tsx

@@ -17,9 +17,9 @@ export const metadata: Metadata = {
 };
 
 export default async function WiderrufPage() {
-  const page = await getLegalPage("widerruf");
-  const headings = page ? extractHeadings(page.content) : [];
   const { isEnabled: isPreview } = await draftMode();
+  const page = await getLegalPage("widerruf", { draft: isPreview });
+  const headings = page ? extractHeadings(page.content) : [];
 
   return (
     <>