feat(F-161): completed feature

project/src/app/build-app.ts

@@ -342,7 +342,9 @@ export async function buildApp(deps: BuildAppDeps = {}): Promise<FastifyInstance
     await app.register(async (instance) => {
       await registerCheckoutRoutes(instance, {
         pool: deps.pool as pg.Pool,
-        authenticate: combinedAuth,
+        // Checkout creates customer-owned orders. Do not use combinedAuth here:
+        // a coexisting backoffice cookie must never override the storefront user.
+        authenticate,
         tracer: telemetry.tracer,
       });
     });