Enhance checkout flow with new components and validation

- Added AddressForm and CheckoutForm components for user input during checkout.
- Implemented validation using Zod and VeeValidate for billing address fields.
- Created OrderSummary and MockPayPalButton components for order confirmation and payment simulation.
- Updated CartSheet and CartSidebar to navigate to the new checkout page at '/kasse'.
- Introduced new API endpoints for validating checkout data and creating orders.
- Enhanced user experience with responsive design and error handling.

These changes complete the checkout functionality, allowing users to enter billing information, simulate payment, and confirm orders.

server/api/orders/confirm/[id].post.ts

@@ -0,0 +1,85 @@
+/**
+ * POST /api/orders/confirm/[id]
+ *
+ * Confirm an order after mock payment
+ *
+ * Security:
+ * - Requires authentication
+ * - Users can only confirm their own orders
+ * - Order must be in 'pending' status
+ *
+ * Behavior:
+ * - Updates order status: 'pending' → 'completed'
+ * - Stores completion timestamp
+ * - Clears user's cart
+ * - Returns order details
+ *
+ * Response:
+ * {
+ *   success: true
+ *   order: Order
+ *   message: string
+ * }
+ */
+
+import { eq, and } from 'drizzle-orm'
+import { orders, cartItems } from '../../../database/schema'
+
+export default defineEventHandler(async (event) => {
+  // Require authentication
+  const { user } = await requireUserSession(event)
+
+  // Get order ID from URL parameter
+  const orderId = getRouterParam(event, 'id')
+
+  if (!orderId) {
+    throw createError({
+      statusCode: 400,
+      statusMessage: 'Order ID is required',
+    })
+  }
+
+  const db = useDatabase()
+
+  // Fetch order
+  const order = await db.query.orders.findFirst({
+    where: and(eq(orders.id, orderId), eq(orders.userId, user.id)),
+  })
+
+  if (!order) {
+    throw createError({
+      statusCode: 404,
+      statusMessage: 'Order not found',
+    })
+  }
+
+  // Validate order status
+  if (order.status !== 'pending') {
+    throw createError({
+      statusCode: 400,
+      statusMessage: `Order cannot be confirmed. Current status: ${order.status}`,
+    })
+  }
+
+  // Update order status to completed
+  const [updatedOrder] = await db
+    .update(orders)
+    .set({
+      status: 'completed',
+      paymentCompletedAt: new Date(),
+      paymentId: `MOCK-${Date.now()}`, // Mock payment ID
+      updatedAt: new Date(),
+    })
+    .where(eq(orders.id, orderId))
+    .returning()
+
+  // Clear user's cart
+  const cart = await getOrCreateCart(event)
+  await db.delete(cartItems).where(eq(cartItems.cartId, cart.id))
+
+  return {
+    success: true,
+    order: updatedOrder,
+    message: 'Bestellung erfolgreich bestätigt',
+  }
+})