Add Postman Collection for API Endpoints

[MuhammadSaim]

Summary

• Added a new Postman collection to the project for easier testing and documentation of API endpoints.

Details

• Collection includes all current API routes with example requests and descriptions where applicable.
• This will help both internal developers and external collaborators to understand and test the API quickly.

Notes

• The file is added under ./lua.sh.postman_collection.json.
• Future API changes should also update this collection to keep it in sync.

[paulocastellano]

Good job @MuhammadSaim!