[Feature] Add API documentation with Swagger/OpenAPI

[Open-Source-you]

Is your feature request related to a problem? Please describe.
Developers lack a clear reference for backend API endpoints.

Describe the solution you'd like
Generate and publish API documentation using Swagger or OpenAPI.

Describe alternatives you've considered
Manual documentation, but automated tools are more maintainable.

Additional context
Comprehensive docs will help backend and frontend teams collaborate.

[Raja-89]

Please Assign thi issue to me, looks intersting to work upon