feat: Wabenhain Honig-Shop Anwendung

Vollstaendige Next.js/Prisma-E-Commerce-Anwendung fuer eine Imkerei:
Shop, Warenkorb, Stripe-Checkout, Kundenkonto mit 2FA, Admin-Bereich
(Produkte, Ernten, Chargen, Bestellungen, Gutscheine, admin-editierbare
Website-Inhalte), i18n (DE/EN), Rate-Limiting/CSP/Audit-Log-Haertung,
PostgreSQL- und MySQL-Unterstuetzung ueber austauschbare Prisma-
Treiber-Adapter, Unit-/Komponenten-/E2E-Tests.

src/app/checkout/checkout-form.test.tsx

@@ -0,0 +1,58 @@
+import { describe, test, expect, beforeEach, vi } from "vitest";
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { CheckoutForm } from "./checkout-form";
+import { useCartStore, type CartItem } from "@/store/cart-store";
+import { I18nProvider } from "@/i18n/i18n-provider";
+import type { ShippingTierLike } from "@/lib/shipping-calc";
+import type { BulkDiscountTierLike } from "@/lib/bulk-discount-calc";
+
+vi.mock("next/navigation", () => ({
+  useRouter: () => ({ push: vi.fn() }),
+}));
+
+const tiers: ShippingTierLike[] = [{ minQuantity: 0, maxQuantity: null, priceCents: 700 }];
+const bulkDiscountTiers: BulkDiscountTierLike[] = [];
+
+const item = (overrides: Partial<CartItem> = {}): CartItem => ({
+  productId: "p1",
+  slug: "fruehtracht-2026",
+  name: "Frühtracht 2026",
+  weightGrams: 500,
+  priceCents: 990,
+  image: null,
+  quantity: 1,
+  ...overrides,
+});
+
+function renderCheckout(items: CartItem[]) {
+  useCartStore.setState({ items, isOpen: false });
+  return render(
+    <I18nProvider locale="de">
+      <CheckoutForm tiers={tiers} bulkDiscountTiers={bulkDiscountTiers} />
+    </I18nProvider>
+  );
+}
+
+beforeEach(() => {
+  useCartStore.setState({ items: [], isOpen: false });
+});
+
+describe("CheckoutForm", () => {
+  test("shows the empty-cart message instead of the form when the cart is empty", () => {
+    renderCheckout([]);
+    expect(screen.queryByRole("button", { name: /kostenpflichtig bestellen/i })).not.toBeInTheDocument();
+  });
+
+  test("charges shipping by default and drops it when switching to pickup", async () => {
+    const userEventInstance = userEvent.setup();
+    renderCheckout([item()]);
+
+    expect(screen.getByText("7,00 €")).toBeInTheDocument();
+
+    await userEventInstance.click(screen.getByRole("button", { name: /abholung/i }));
+
+    expect(screen.queryByText("7,00 €")).not.toBeInTheDocument();
+    expect(screen.getByText("kostenlos")).toBeInTheDocument();
+  });
+});