Fix order complete: update fulfillment state alongside order state

Square requires all fulfillments to be COMPLETED before the order can be
marked COMPLETED — include fulfillment state in the same updateOrder call.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

estore/src/app/api/admin/orders/[orderId]/complete/route.ts

@@ -24,9 +24,13 @@ export async function POST(
 
     await client.ordersApi.updateOrder(orderId, {
       order: {
-        locationId: order.locationId!,
+        locationId:   order.locationId!,
-        state:      'COMPLETED',
+        state:        'COMPLETED',
-        version:    order.version,
+        version:      order.version,
+        fulfillments: (order.fulfillments ?? []).map((f) => ({
+          uid:   f.uid,
+          state: 'COMPLETED',
+        })),
       },
       idempotencyKey: `complete-${orderId}`,
     })