feat: refactor configuration to use environment variables and add .env support

[A69SHUBHAM]

Summary

This PR refactors the project configuration to use environment variables instead of hardcoded values, improving security and maintainability.

Changes

• Moved configuration values (API URLs, settings) to .env
• Added .env.example file for reference
• Updated backend to read environment variables using python-dotenv
• Removed hardcoded configuration from source code
• Updated README with setup instructions

Why this is needed

Hardcoded configuration makes the project less secure and harder to manage across environments. Using environment variables follows best practices and allows flexible configuration for development and production.

Testing

• Verified application runs correctly with .env file
• Tested missing variables → proper fallback or error handling
• Confirmed no hardcoded values remain in the codebase

Impact

• Improves security by avoiding hardcoded sensitive values
• Enhances maintainability and scalability
• Makes setup easier for contributors

Closes #29