feat: enhance order asset selection and previews

tests/app/api/orders-create.route.test.ts

@@ -158,3 +158,63 @@ test("normalizes upstream validation errors from the backend", async () => {
     },
   });
 });
+
+test("accepts order creation payloads without a scene asset id", async () => {
+  vi.stubEnv("BACKEND_BASE_URL", "http://backend.test/api/v1");
+
+  const fetchMock = vi.fn().mockResolvedValue(
+    new Response(
+      JSON.stringify({
+        order_id: 88,
+        workflow_id: "wf-88",
+        status: "created",
+      }),
+      {
+        status: 201,
+        headers: {
+          "content-type": "application/json",
+        },
+      },
+    ),
+  );
+
+  vi.stubGlobal("fetch", fetchMock);
+
+  const request = new Request("http://localhost/api/orders", {
+    method: "POST",
+    headers: {
+      "content-type": "application/json",
+    },
+    body: JSON.stringify({
+      customer_level: "low",
+      service_mode: "auto_basic",
+      model_id: 101,
+      garment_asset_id: 303,
+    }),
+  });
+
+  const response = await POST(request);
+  const payload = await response.json();
+
+  expect(response.status).toBe(201);
+  expect(payload).toEqual({
+    mode: "proxy",
+    data: {
+      orderId: 88,
+      workflowId: "wf-88",
+      status: "created",
+    },
+  });
+  expect(fetchMock).toHaveBeenCalledWith(
+    "http://backend.test/api/v1/orders",
+    expect.objectContaining({
+      method: "POST",
+      body: JSON.stringify({
+        customer_level: "low",
+        service_mode: "auto_basic",
+        model_id: 101,
+        garment_asset_id: 303,
+      }),
+    }),
+  );
+});