Consolidate Kreditkarte/PayPal into one "Online-Zahlung" checkout option

Both already route through the same Stripe PaymentIntent
(automatic_payment_methods: enabled — Stripe's own recommended Payment
Element pattern, letting Stripe itself decide which eligible method to
show). Pre-selecting one of two identical-behind-the-scenes rows before
the payment step was redundant friction, not a real choice. Collapses
them into one option with a hint text explaining the actual instrument
is picked on the next screen; Überweisung is unaffected.

Also refines paymentMethodTitle from a neutral "Online-Zahlung"
placeholder (snapshotted at order-creation time, before the customer has
picked an instrument) to the real one Stripe reports, once payment
confirms — carried through to both the stored order and the
sessionStorage snapshot shown on /bestellbestaetigung.

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

app/lib/payments/stripeProvider.ts

@@ -49,6 +49,29 @@ async function attachOrderMetadata(providerReference: string, metadata: { orderI
 
 export const stripeProvider: PaymentProvider = { createPaymentIntent, attachOrderMetadata };
 
+const PAYMENT_METHOD_LABELS: Record<string, string> = { card: "Kreditkarte", paypal: "PayPal" };
+
+// Called only by the real webhook route on `payment_intent.succeeded` —
+// the checkout route snapshots a neutral "Online-Zahlung" title at order
+// creation (see its own comment: the customer hasn't chosen an instrument
+// yet at that point, Stripe's Payment Element does that next), this
+// resolves the actual one once Stripe reports it so the order/invoice/
+// confirmation email reflect what was really used, not a placeholder.
+// Best-effort: an unresolvable label just leaves the neutral title in
+// place (confirmPayment.ts only overwrites paymentMethodTitle when this
+// returns something), it doesn't fail the payment confirmation itself.
+export async function resolveStripePaymentMethodLabel(intent: Stripe.PaymentIntent): Promise<string | undefined> {
+  const pm = intent.payment_method;
+  const pmId = typeof pm === "string" ? pm : pm?.id;
+  if (!pmId) return undefined;
+  try {
+    const resolved = pm && typeof pm === "object" ? pm : await getClient().paymentMethods.retrieve(pmId);
+    return PAYMENT_METHOD_LABELS[resolved.type] ?? resolved.type;
+  } catch {
+    return undefined;
+  }
+}
+
 // Only used by the real webhook route (never through the PaymentProvider
 // interface — signature verification is inherently Stripe-shaped, no
 // other provider exists to share this contract with yet).