Move low-stock hint to badge, right-align VAT breakdown, gate cart discount field, split billing/shipping delivery method

- Removed the inline "Nur noch wenige verfügbar" text hint from
  AddToCartButton/AddToCartInlineButton (was making card heights vary in
  every grid that renders them — RelatedProducts, ProductSpotlight's CTA
  row) — now only shown via the same image-overlaid pill badge
  Ausverkauft/discount already use (position: absolute, doesn't affect
  layout). Added that badge to RelatedProducts.tsx and todo-cards'
  Pricing.tsx, which didn't have it before.
- RelatedProducts cards now also show "inkl. X% MwSt." (was missing
  entirely)
- VatBreakdown rows are now flex rows with a spacer instead of plain
  text, so every € amount right-aligns to the same edge regardless of
  how many digits the rate itself has (was visibly staggered with mixed
  7%/19% rates)
- Cart's manual discount-code field only renders when Payload actually
  has at least one active code right now (lib/discountServer.ts's new
  hasActiveDiscountCode()) — no point showing an open field that could
  never validate. An already-applied code (e.g. from an older session)
  still always shows its own result row regardless.
- Checkout's "1. Rechnungsadresse" no longer offers a Packstation option
  — a Packstation isn't a valid billing address for an invoice. Only a
  plain street address now; Packstation is only offered on the separate,
  optional "Abweichende Lieferadresse" section, which already had its own
  address/Packstation toggle.

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

app/cart/page.tsx

@@ -5,6 +5,7 @@ import { RelatedProducts } from "./components/RelatedProducts";
 import { TrustRow } from "../components/TrustRow";
 import { Footer } from "../components/Footer";
 import { getCartTrustBadges, getShippingMethods, getShippingSettings, getDefaultTaxRatePercent } from "../lib/payload";
+import { hasActiveDiscountCode } from "../lib/discountServer";
 
 // robots: noindex — transactional page (mirrors a specific shopper's cart
 // contents), per the figma-to-nextjs skill's Step 5 guidance: indexing
@@ -19,11 +20,12 @@ export const metadata: Metadata = {
 };
 
 export default async function CartPage() {
-  const [trustBadges, shippingMethods, shipping, defaultTaxRate] = await Promise.all([
+  const [trustBadges, shippingMethods, shipping, defaultTaxRate, showDiscountField] = await Promise.all([
     getCartTrustBadges(),
     getShippingMethods(),
     getShippingSettings(),
     getDefaultTaxRatePercent(),
+    hasActiveDiscountCode(),
   ]);
 
   // The cart doesn't ask which shipping method the shopper wants yet
@@ -53,9 +55,10 @@ export default async function CartPage() {
             freeShippingThreshold={freeShippingThreshold}
             shippingSettings={shipping}
             defaultTaxRate={defaultTaxRate}
+            showDiscountField={showDiscountField}
           />
         </Suspense>
-        <RelatedProducts />
+        <RelatedProducts defaultTaxRate={defaultTaxRate} />
         <TrustRow />
       </main>
       <Footer />