Checkout‑Registrierung validiert jetzt die E‑Mail‑Länge, und die Checkout‑Flows sind Paddle‑only: Stripe‑Endpoints/

Services/Helpers sind entfernt, API/Frontend angepasst, Tests auf Paddle umgestellt. Außerdem wurde die CSP gestrafft
  und Stripe‑Texte in den Abandoned‑Checkout‑Mails ersetzt.

tests/ui/admin/tenant-onboarding-flow.test.ts

@@ -6,7 +6,7 @@ import { test, expectFixture as expect } from '../helpers/test-fixtures';
  * This suite is currently skipped until we have stable seed data and
  * authentication helpers for Playwright. Once those are in place we can
  * remove the skip and let the flow exercise the welcome -> packages -> summary
- * steps with mocked Stripe/Paddle APIs.
+ * steps with mocked Paddle APIs.
  */
 test.describe('Tenant Onboarding Welcome Flow', () => {
   test('redirects unauthenticated users to login', async ({ page }) => {
@@ -47,16 +47,7 @@ test.describe('Tenant Onboarding Welcome Flow', () => {
     await expect(page).toHaveURL(/\/event-admin\/welcome\/summary/);
     await expect(page.getByRole('heading', { name: /Bestellübersicht/i })).toBeVisible();
 
-    // Validate payment sections. Depending on env we either see Stripe/Paddle widgets or configuration warnings.
-    const stripeConfigured = Boolean(process.env.VITE_STRIPE_PUBLISHABLE_KEY);
-    if (stripeConfigured) {
-      await expect(page.getByRole('heading', { name: /Kartenzahlung \(Stripe\)/i })).toBeVisible();
-    } else {
-      await expect(
-        page.getByText(/Stripe nicht verfügbar|PaymentIntent konnte nicht erstellt werden|Publishable Key fehlt/i)
-      ).toBeVisible();
-    }
-
+    // Validate Paddle payment section.
     await expect(page.getByRole('heading', { name: /^Paddle$/i })).toBeVisible();
 
     // Continue to the setup step without completing a purchase.