Dynamic AGB address, real shipping costs on /versand instead of hardcoded constants

- AGB: name/address/email now come from company-settings via new
  VertragspartnerBlock (mid-document, see LegalPages.ts's contentPart2).
- VersandSections/VersandModal/CartContent/CheckoutContent/versand page:
  shipping cost and free-shipping threshold now come from the real
  ShippingMethods data (already fetched elsewhere for checkout), not the
  hardcoded lib/shipping.ts constants — those had already drifted from
  the real Payload values once. lib/shipping.ts deleted, nothing left to
  export.

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

app/agb/components/VertragspartnerBlock.tsx

@@ -0,0 +1,59 @@
+import { headingId } from "../../components/RichText";
+import type { CompanySettings } from "../../lib/payload";
+import type { TOCSection } from "../../components/SectionTOC";
+
+// Renders "2. Vertragspartner" straight from company-settings, same
+// single-source-of-truth pattern as Impressum's AnbieterAngaben.tsx and
+// Datenschutz's VerantwortlicherBlock.tsx — this used to be hand-typed
+// name/address/email baked into the AGB richText (seed-agb.ts on the
+// Payload side), and had already drifted from the real company-settings
+// values once (the richText's placeholder "Björn Wendt"/"Musterstraße
+// 12" never got updated when the real address was set). Sits mid-document
+// (section 1 "Geltungsbereich" comes before it), which is why AGB's
+// content is split into `content` (section 1) + `contentPart2` (sections
+// 3 onward) rather than just prepending this block like Datenschutz did —
+// see LegalPages.ts's `contentPart2` field comment.
+export function vertragspartnerHeadings(): TOCSection[] {
+  return [{ id: headingId("2. Vertragspartner"), title: "2. Vertragspartner" }];
+}
+
+function Heading({ children }: { children: string }) {
+  return (
+    <h2
+      id={headingId(children)}
+      className="font-semibold text-h-small text-text-primary mt-2 scroll-mt-32 first:mt-0"
+      style={{ fontFamily: "var(--font-lora)" }}
+    >
+      {children}
+      <span className="block h-[0.125rem] w-8 bg-brand mt-2" aria-hidden />
+    </h2>
+  );
+}
+
+function P({ children }: { children: React.ReactNode }) {
+  return <p className="text-body text-text-body">{children}</p>;
+}
+
+export function VertragspartnerBlock({ seller }: { seller: CompanySettings }) {
+  return (
+    <div className="flex flex-col gap-4 w-full">
+      <Heading>2. Vertragspartner</Heading>
+      <P>Der Kaufvertrag kommt zustande mit:</P>
+      <div className="flex flex-col gap-1">
+        <P>
+          <strong>einfach produktiv. – {seller.sellerName}</strong>
+        </P>
+        <P>
+          <strong>
+            {seller.sellerStreet}, {seller.sellerZip} {seller.sellerCity}
+          </strong>
+        </P>
+        <P>
+          <strong>
+            E-Mail: <a href={`mailto:${seller.sellerEmail}`} className="hover:underline">{seller.sellerEmail}</a>
+          </strong>
+        </P>
+      </div>
+    </div>
+  );
+}