Add .env.example files for Client and Server

[VamikaSharma19]

Description:
Currently, the project does not include .env.example files in either the client or server folder. Adding these files will help new contributors easily understand which environment variables are required to run the project locally.

Proposed Changes:
Client (client/.env.example) -
VITE_API_URL=http://localhost:5000

Server (server/.env.example) -
PORT=5000
MONGO_URI=your_mongodb_connection_string
JWT_SECRET=your_jwt_secret_key

Why is this needed?
Makes it easier for contributors to set up the project.
Improves onboarding experience and documentation quality.
Follows best practices for open-source projects.

Additional Notes:
This is a beginner-friendly but important improvement that will help maintainers and contributors run the project seamlessly.

I would be happy to work on this issue. Could you please assign it to me?

[github-actions]

Thank you for raising this issue!

We'll review it as soon as possible. We truly appreciate your contributions! ✨

Meanwhile make sure you've visited the README.md, CONTRIBUTING.md, and CODE_OF_CONDUCT.md before creating a PR for this. Also, please do NOT create a PR until this issue has been assigned to you. 😊

[VamikaSharma19]

Hey @GollaBharath, please assign this issue to me.

[DeadIndian]

Alright... go ahead :)

[DeadIndian]

@VamikaSharma19 what event are you from?

[DeadIndian]

Also please follow the default template from next time... its easier for us to review

[VamikaSharma19]

Hello @GollaBharath, I'm a OSCI contributor. Thank you so much for assigning me this issue. Next time i will make sure to keep all instructions in mind.