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/todo-cards/components/Pricing.tsx

@@ -26,6 +26,9 @@ export async function Pricing() {
   if (!product) return null;
   const discount = discountPercent(product.price, product.compareAtPrice);
   const taxRate = effectiveTaxRate(product, defaultTaxRate);
+  // Same "any vs. every" split as ProductGrid.tsx/ProductSpotlight.tsx.
+  const fullyOutOfStock = product.variants.length > 0 ? product.variants.every((v) => v.outOfStock) : product.outOfStock;
+  const anyLowStock = product.variants.length > 0 ? product.variants.some((v) => v.lowStock) : product.lowStock;
 
   return (
     <section className="w-full bg-bg-base px-[var(--layout-padding-x)] py-8">
@@ -41,10 +44,20 @@ export async function Pricing() {
             sizes="(min-width: 1024px) 410px, 100vw"
             className="object-cover transition-transform duration-500 group-hover:scale-105"
           />
-          {discount !== null && (
+          {fullyOutOfStock ? (
+            <span className="absolute top-3 left-3 rounded-full bg-text-muted px-2.5 py-1 text-label font-bold text-bg-base">
+              Ausverkauft
+            </span>
+          ) : discount !== null ? (
             <span className="absolute top-3 left-3 rounded-full bg-brand px-2.5 py-1 text-label font-bold text-text-primary">
               -{discount}%
             </span>
+          ) : (
+            anyLowStock && (
+              <span className="absolute top-3 left-3 rounded-full bg-warning px-2.5 py-1 text-label font-bold text-text-on-dark">
+                Nur noch wenige verfügbar
+              </span>
+            )
           )}
         </div>
 
@@ -86,7 +99,6 @@ export async function Pricing() {
             label="In den Warenkorb"
             className="w-full inline-flex items-center justify-center px-6 py-[0.8125rem] rounded-sm bg-brand hover:bg-brand-hover active:scale-[0.97] transition-all font-bold text-body text-text-primary text-center focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-brand focus-visible:ring-offset-2 focus-visible:ring-offset-bg-muted"
             outOfStock={product.outOfStock}
-            lowStock={product.lowStock}
             variants={product.variants}
           />
         </div>

app/todo-cards/components/TodoKartenHero.tsx

@@ -114,7 +114,7 @@ export async function TodoKartenHero() {
             </div>
 
             {product && (
-              <AddToCartButton label="ToDo-Karten bestellen" outOfStock={product.outOfStock} lowStock={product.lowStock} variants={product.variants} />
+              <AddToCartButton label="ToDo-Karten bestellen" outOfStock={product.outOfStock} variants={product.variants} />
             )}
           </div>
         </Reveal>