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/checkout/components/CheckoutContent.tsx

@@ -70,7 +70,6 @@ export function CheckoutContent({
   const [shippingMethodId, setShippingMethodId] = useState<number | null>(shippingMethods[0]?.id ?? null);
   const [paymentMethodId, setPaymentMethodId] = useState<number | null>(paymentMethods[0]?.id ?? null);
   const [versandOpen, setVersandOpen] = useState(false);
-  const [deliveryMethod, setDeliveryMethod] = useState<"address" | "packstation">(savedProfile?.deliveryMethod ?? "address");
   const [purchaseError, setPurchaseError] = useState<string | null>(null);
   const [purchasing, setPurchasing] = useState(false);
   const [showLogin, setShowLogin] = useState(false);
@@ -90,9 +89,10 @@ export function CheckoutContent({
   const [firstName, setFirstName] = useState(savedProfile?.firstName ?? "");
   const [lastName, setLastName] = useState(savedProfile?.lastName ?? "");
   const [email, setEmail] = useState(savedProfile?.email ?? customerEmail ?? "");
+  // Always a plain street address — a Packstation isn't a valid Rechnungs-
+  // adresse (an invoice needs a real postal address). Packstation is only
+  // ever offered on the separate, optional shipping-address override below.
   const [street, setStreet] = useState(savedProfile?.street ?? "");
-  const [packstationNumber, setPackstationNumber] = useState(savedProfile?.packstationNumber ?? "");
-  const [postNumber, setPostNumber] = useState(savedProfile?.postNumber ?? "");
   const [zip, setZip] = useState(savedProfile?.zip ?? "");
   const [city, setCity] = useState(savedProfile?.city ?? "");
   const [country, setCountry] = useState(savedProfile?.country ?? "Deutschland");
@@ -130,10 +130,7 @@ export function CheckoutContent({
       if (draft.firstName) setFirstName(draft.firstName);
       if (draft.lastName) setLastName(draft.lastName);
       if (draft.email) setEmail(draft.email);
-      if (draft.deliveryMethod) setDeliveryMethod(draft.deliveryMethod);
       if (draft.street) setStreet(draft.street);
-      if (draft.packstationNumber) setPackstationNumber(draft.packstationNumber);
-      if (draft.postNumber) setPostNumber(draft.postNumber);
       if (draft.zip) setZip(draft.zip);
       if (draft.city) setCity(draft.city);
       if (draft.country) setCountry(draft.country);
@@ -161,10 +158,7 @@ export function CheckoutContent({
       firstName,
       lastName,
       email,
-      deliveryMethod,
       street,
-      packstationNumber,
-      postNumber,
       zip,
       city,
       country,
@@ -187,10 +181,7 @@ export function CheckoutContent({
     firstName,
     lastName,
     email,
-    deliveryMethod,
     street,
-    packstationNumber,
-    postNumber,
     zip,
     city,
     country,
@@ -317,10 +308,10 @@ export function CheckoutContent({
       // one address-card field that stays uncontrolled/unpersisted (see
       // lib/checkoutDraft.ts's own comment on why).
       password: customerEmail ? undefined : String(form.get("password") ?? ""),
-      deliveryMethod,
+      // Rechnungsadresse is always a plain street address — see the
+      // street state's own comment on why Packstation isn't offered here.
+      deliveryMethod: "address" as const,
       street: street || undefined,
-      packstationNumber: packstationNumber || undefined,
-      postNumber: postNumber || undefined,
       zip,
       city,
       country,
@@ -547,79 +538,21 @@ export function CheckoutContent({
                 </p>
               </div>
             )}
-            {/* Segmented control, same sm:w-[calc(50%-0.5rem)] half-row
-                width as the field(s) below it — Lieferadresse keeps
-                Straße und Hausnummer, Packstation swaps it out for
-                Packstationnummer + Postnummer (DHL's two Packstation
-                identifiers; there's no house number to give). */}
-            <div className="w-full sm:w-[calc(50%-0.5rem)] flex flex-col gap-2 items-start">
-              <span className="text-label text-text-muted">Lieferart</span>
-              <div className="flex w-full rounded-sm border border-border overflow-hidden">
-                <button
-                  type="button"
-                  onClick={() => setDeliveryMethod("address")}
-                  aria-pressed={deliveryMethod === "address"}
-                  className={`flex-1 py-3 text-body-sm font-bold transition-colors ${
-                    deliveryMethod === "address"
-                      ? "bg-brand text-text-primary"
-                      : "text-text-muted hover:text-text-primary"
-                  }`}
-                >
-                  Lieferadresse
-                </button>
-                <button
-                  type="button"
-                  onClick={() => setDeliveryMethod("packstation")}
-                  aria-pressed={deliveryMethod === "packstation"}
-                  className={`flex-1 py-3 text-body-sm font-bold border-l border-border transition-colors ${
-                    deliveryMethod === "packstation"
-                      ? "bg-brand text-text-primary"
-                      : "text-text-muted hover:text-text-primary"
-                  }`}
-                >
-                  Packstation
-                </button>
-              </div>
-            </div>
-
-            {deliveryMethod === "address" ? (
-              <FormField
-                label="Straße und Hausnummer"
-                name="street"
-                type="text"
-                value={street}
-                onChange={(e) => setStreet(e.target.value)}
-                placeholder="Musterstraße 1"
-                autoComplete="street-address"
-                required
-                wrapperClassName="w-full sm:w-[calc(50%-0.5rem)] sm:flex-none min-w-0"
-              />
-            ) : (
-              <div className="flex flex-col sm:flex-row gap-4 w-full">
-                <FormField
-                  label="Packstationnummer"
-                  name="packstationNumber"
-                  type="text"
-                  value={packstationNumber}
-                  onChange={(e) => setPackstationNumber(e.target.value)}
-                  inputMode="numeric"
-                  placeholder="123"
-                  autoComplete="off"
-                  required
-                />
-                <FormField
-                  label="Postnummer"
-                  name="postNumber"
-                  type="text"
-                  value={postNumber}
-                  onChange={(e) => setPostNumber(e.target.value)}
-                  inputMode="numeric"
-                  placeholder="1234567"
-                  autoComplete="off"
-                  required
-                />
-              </div>
-            )}
+            {/* Always a plain street address — Packstation isn't a valid
+                Rechnungsadresse (an invoice needs a real postal address).
+                Packstation is only ever offered below, in the optional
+                "Abweichende Lieferadresse" section's own Lieferart toggle. */}
+            <FormField
+              label="Straße und Hausnummer"
+              name="street"
+              type="text"
+              value={street}
+              onChange={(e) => setStreet(e.target.value)}
+              placeholder="Musterstraße 1"
+              autoComplete="street-address"
+              required
+              wrapperClassName="w-full sm:w-[calc(50%-0.5rem)] sm:flex-none min-w-0"
+            />
             <div className="flex flex-col sm:flex-row gap-4 w-full">
               <FormField label="PLZ" name="zip" type="text" value={zip} onChange={(e) => setZip(e.target.value)} placeholder="10115" autoComplete="postal-code" required />
               <FormField label="Ort" name="city" type="text" value={city} onChange={(e) => setCity(e.target.value)} placeholder="Berlin" autoComplete="address-level2" required />