Critical: Backend crashing due to deprecated Groq model (gemma2-9b-it)

[Prabhatyadav60]

The backend is currently throwing groq.BadRequestError because the gemma2-9b-it model has been decommissioned by Groq.

Impact: All Bias, Chat, and Fact-Check modules are failing. Solution: We need to upgrade to llama-3.3-70b-versatile immediately.

I have raised a PR to fix this.