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/components/VatBreakdown.tsx

@@ -4,24 +4,34 @@ import type { TaxBreakdownGroup } from "../lib/taxBreakdown";
 // The actual amount of VAT included in a total — not just a disclosure
 // that VAT is included (see cartTotals.ts's effectiveTaxRate() for the
 // "which %" shown next to each line item elsewhere). One line per rate
-// when a cart/order spans more than one; a single line otherwise.
+// when a cart/order spans more than one; a single line otherwise. Each
+// line is a flex row with a spacer (same "label, flex-1 spacer, value"
+// shape as every other Zwischensumme/Versand/Gesamtsumme row in the
+// sidebars this renders inside) so every € amount lands on the same
+// right-hand edge — a plain "X%: Y €" text line left the amount starting
+// wherever the rate's own digit count happened to end, visibly misaligned
+// as soon as two different rates (e.g. "7%" vs "19%") were both present.
 export function VatBreakdown({ groups }: { groups: TaxBreakdownGroup[] }) {
   if (groups.length === 0) return null;
   if (groups.length === 1) {
     const [g] = groups;
     return (
-      <p className="text-label text-text-muted">
-        enthält {g.rate}% MwSt.: {formatPrice(g.tax)}
-      </p>
+      <div className="flex items-center w-full">
+        <span className="text-label text-text-muted">enthält {g.rate}% MwSt.</span>
+        <span className="flex-1" />
+        <span className="text-label text-text-muted">{formatPrice(g.tax)}</span>
+      </div>
     );
   }
   return (
-    <div className="flex flex-col gap-0.5">
+    <div className="flex flex-col gap-0.5 w-full">
       <p className="text-label text-text-muted">enthält MwSt.:</p>
       {groups.map((g) => (
-        <p key={g.rate} className="text-label text-text-muted pl-2">
-          {g.rate}%: {formatPrice(g.tax)}
-        </p>
+        <div key={g.rate} className="flex items-center w-full pl-2">
+          <span className="text-label text-text-muted">{g.rate}%</span>
+          <span className="flex-1" />
+          <span className="text-label text-text-muted">{formatPrice(g.tax)}</span>
+        </div>
       ))}
     </div>
   );