Secure OpenAI API Integration

To strengthen platform security and reliability, Decode now routes all AI requests through a secure backend service rather than handling them directly. AI requests are now processed through this backend, which improves how requests are handled while keeping API credentials protected rather than exposed elsewhere in the system.

This change is meant to give a more secure, reliable foundation for AI-powered features across the platform going forward, without changing what those features actually do from a researcher's point of view.