Add comprehensive README and .env.example files

The project currently lacks clear and complete documentation for setup and configuration, which makes it difficult for new contributors to get started.

Several key pieces of documentation are missing or incomplete, especially around environment configuration and backend setup.

### Missing / Incomplete Documentation

#### README Improvements Needed

* **Main README**

* Missing clear setup instructions
* No quick start guide
* Prerequisites and dependencies are not clearly listed
* **Backend README**

* API endpoints are not documented
* Backend dependencies are unclear
* Configuration and environment setup is missing

#### Missing `.env.example` File

* No `.env.example` file exists in the backend directory
* Required environment variables (API keys, secrets, config values) are not documented
* New developers must guess which environment variables are needed and what they are used for

### Suggested Solution

* Add a `.env.example` file in the **backend** directory containing:

* All required environment variables
* Dummy or placeholder values
* Inline comments explaining the purpose of each variable
* Update the **main README** to include:

* Quick start guide
* Setup instructions for both frontend and backend
* Required prerequisites and dependencies
* Improve the **backend README** by documenting:

* API endpoints
* Backend dependencies
* Configuration steps

### Benefits

* Easier onboarding for new contributors
* Reduced setup and troubleshooting time
* Fewer configuration-related issues
* Improved developer experience overall

@ParagGhatage Please assign this issue to me. I’d like to work on it.