Tattle: integrate with kaapi-backend

[kartpop]

Is your feature request related to a problem? Please describe.

While the kaapi-guardrails service has been deployed with basic endpoints and 3-4 validators, kaapi users cannot currently benefit from these validation capabilities. The service is not integrated with kaapi-backend's LLM interaction endpoints or configuration management system. This means:

• Users cannot access guardrails validation through llm interaction endpoints
• Validation capabilities remain isolated and unusable

Describe the solution you'd like

Integrate kaapi-guardrails with kaapi-backend to enable user-facing guardrails functionality:

1. LLM Pipeline Integration

   • Integrate guardrails validation into LLM interaction endpoint
   • Make validation calls asynchronous and non-blocking
   • Implement proper error handling and fallback behavior

2. Configuration Management Integration

   • Add guardrails configuration options to existing config management endpoints
   • Enable users to select which validators to apply
   • Support project-level validator settings
   • Add endpoints to list available validators