Context An Express API receives user-submitted data that is passed directly to database queries without validation, exposing the application to injection and data integrity issues. The Problem No input validation is performed on incoming request bodies, query parameters, or route parameters. Constraints Define validation schemas for request bodies and query parameters using Zod or Joi. Create a reusable validation middleware that applies the schema and returns 422 with detailed error messages on failure. Apply the middleware to at least three routes. Expected Deliverable An Express API with a reusable schema validation middleware using Zod or Joi, returning structured 422 error responses for invalid inputs.