Blog categories (hasMany), shipping-address contact fields, product SKU on invoices

- Posts.categories is now hasMany — blog list/detail/live-preview render
  a comma-joined list instead of a single category.
- Checkout's "Abweichende Lieferadresse" gains optional Firma + Kontakt-
  E-Mail/Telefon fields (handed to the shipping carrier, not used for
  customer communication).
- Customer profile can now store its own shipping address (mirroring
  Customers.ts's new "Lieferadresse" tab), prefilling the checkout
  override instead of always starting blank.
- Product-level optional SKU (previously only on variants) snapshots onto
  each order item and shows up on invoices (visual + EN16931 XML),
  the confirmation email, and the account order detail page.

app/api/account/profile/route.ts

@@ -13,7 +13,32 @@ export async function PATCH(request: Request) {
   if (!session) return NextResponse.json({ ok: false, reason: "Bitte zuerst einloggen." }, { status: 401 });
 
   const body = await request.json().catch(() => null);
-  const { firstName, lastName, deliveryMethod, street, packstationNumber, postNumber, zip, city, country, companyName, vatId } = body ?? {};
+  const {
+    firstName,
+    lastName,
+    deliveryMethod,
+    street,
+    packstationNumber,
+    postNumber,
+    zip,
+    city,
+    country,
+    companyName,
+    vatId,
+    hasDifferentShippingAddress,
+    shippingFirstName,
+    shippingLastName,
+    shippingCompanyName,
+    shippingDeliveryMethod,
+    shippingStreet,
+    shippingPackstationNumber,
+    shippingPostNumber,
+    shippingZip,
+    shippingCity,
+    shippingCountry,
+    shippingContactEmail,
+    shippingContactPhone,
+  } = body ?? {};
   if (
     typeof firstName !== "string" ||
     !firstName ||
@@ -42,6 +67,33 @@ export async function PATCH(request: Request) {
     return NextResponse.json({ ok: false, reason: "Ungültiges USt-IdNr.-Format (z. B. DE123456789)." }, { status: 400 });
   }
 
+  // Same shape as the checkout's own shipping-address-override validation
+  // (api/checkout/route.ts) — required fields only apply when the toggle
+  // is actually on, since this whole block is optional otherwise.
+  if (hasDifferentShippingAddress) {
+    if (
+      typeof shippingFirstName !== "string" ||
+      !shippingFirstName ||
+      typeof shippingLastName !== "string" ||
+      !shippingLastName ||
+      (shippingDeliveryMethod !== "address" && shippingDeliveryMethod !== "packstation") ||
+      typeof shippingZip !== "string" ||
+      !shippingZip ||
+      typeof shippingCity !== "string" ||
+      !shippingCity ||
+      typeof shippingCountry !== "string" ||
+      !shippingCountry
+    ) {
+      return NextResponse.json({ ok: false, reason: "Bitte alle Pflichtfelder der Lieferadresse ausfüllen." }, { status: 400 });
+    }
+    if (shippingDeliveryMethod === "address" && !shippingStreet) {
+      return NextResponse.json({ ok: false, reason: "Bitte Straße und Hausnummer der Lieferadresse angeben." }, { status: 400 });
+    }
+    if (shippingDeliveryMethod === "packstation" && (!shippingPackstationNumber || !shippingPostNumber)) {
+      return NextResponse.json({ ok: false, reason: "Bitte Packstation- und Postnummer der Lieferadresse angeben." }, { status: 400 });
+    }
+  }
+
   const result = await updateCustomerProfile(session.token, session.customer.id, {
     firstName,
     lastName,
@@ -54,6 +106,19 @@ export async function PATCH(request: Request) {
     country,
     companyName: typeof companyName === "string" && companyName ? companyName : undefined,
     vatId: normalizedVatId,
+    hasDifferentShippingAddress: Boolean(hasDifferentShippingAddress),
+    shippingFirstName: hasDifferentShippingAddress ? shippingFirstName : undefined,
+    shippingLastName: hasDifferentShippingAddress ? shippingLastName : undefined,
+    shippingCompanyName: hasDifferentShippingAddress && shippingCompanyName ? shippingCompanyName : undefined,
+    shippingDeliveryMethod: hasDifferentShippingAddress ? shippingDeliveryMethod : undefined,
+    shippingStreet: hasDifferentShippingAddress ? shippingStreet : undefined,
+    shippingPackstationNumber: hasDifferentShippingAddress ? shippingPackstationNumber : undefined,
+    shippingPostNumber: hasDifferentShippingAddress ? shippingPostNumber : undefined,
+    shippingZip: hasDifferentShippingAddress ? shippingZip : undefined,
+    shippingCity: hasDifferentShippingAddress ? shippingCity : undefined,
+    shippingCountry: hasDifferentShippingAddress ? shippingCountry : undefined,
+    shippingContactEmail: hasDifferentShippingAddress && shippingContactEmail ? shippingContactEmail : undefined,
+    shippingContactPhone: hasDifferentShippingAddress && shippingContactPhone ? shippingContactPhone : undefined,
   });
   return NextResponse.json(result, { status: result.ok ? 200 : 400 });
 }