feat: Add role-based access control tests and fix middleware export

This commit adds comprehensive unit tests for the role-based access control middleware and fixes the ES module export issue. The tests verify that users with correct roles can access protected routes, while users with incorrect roles or no authentication are properly denied access.

backend/middleware/role.middleware.js

@@ -23,4 +23,4 @@ const requireRole = (requiredRoles) => {
   };
 };
 
-module.exports = { requireRole };
+export { requireRole };