refactor: add ApiRoutes import to FileControllerIntegrationTests

Added using statement for JdeScoping.Core.ApiContracts. The existing
routes (/api/file/...) are left unchanged as they test legacy download
by cache key endpoints which differ from the new FileIO routes.

NEW/tests/JdeScoping.Api.IntegrationTests/FileControllerIntegrationTests.cs

@@ -1,5 +1,6 @@
 using System.Net;
 using System.Net.Http.Json;
+using JdeScoping.Core.ApiContracts;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Shouldly;