Frontend shows unclear error when GraphQL client is not configured

## Description

While setting up the OWASP Nest frontend locally, I encountered the following error:

"Configuration Error: GraphQL Client failed to initialize"

This occurs when the GraphQL backend is not configured or running.

## Issue

The current error message is not very informative for new contributors and may cause confusion during onboarding.

## Suggested Improvements

- Provide clearer setup instructions for required backend services
- Improve the error message to indicate that the backend may not be running or environment variables are missing
- Optionally include a fallback or development-friendly message

## Additional Context

This was encountered during initial local setup of the frontend.

I would be happy to work on improving this if it aligns with the project.