Modules

Summary

Organizing a backend codebase into separate files with clear responsibilities (routes, controllers, services, models) using `import`/`export` or `require`.

• 1Split a single large server file into routes, controllers and services modules.
• 2Learn barrel exports (`index.ts` re-exporting a folder's modules) and their trade-offs.
• 3Keep circular dependencies in mind as your module graph grows.