Update src/app.js and register the error handler after all routes.

The final middleware order should be:

1. Security middleware.
2. CORS middleware.
3. Body parsing middleware.
4. API routes.
5. Not-found handler.
6. Error handler.

The not-found handler catches requests that do not match any registered route.

import { errorHandler } from './middleware/error.middleware.js';

app.use('/api/v1', apiRoutes);

app.use((req, res) => {
  res.status(404).json({
    success: false,
    message: `Route not found: ${req.method} ${req.originalUrl}`
  });
});

app.use(errorHandler);