fix(ci): close migration and toxiproxy gates

backend/Program.cs

@@ -1,5 +1,6 @@
 using Nexus.Api.Extensions;
 using Nexus.Api.Http;
+using Microsoft.AspNetCore.DataProtection;
 using System.Reflection;
 
 var builder = WebApplication.CreateBuilder(args);
@@ -11,6 +12,8 @@ if (isOpenApiGeneration)
     // auth services, so use an ephemeral contract-only signing value.
     builder.Configuration["Jwt:Key"] =
         "openapi-contract-generation-only-000000000000000000";
+    builder.Services.AddDataProtection()
+        .UseEphemeralDataProtectionProvider();
 }
 
 // --- Service Registration ---