Add conversation history management and API endpoints

- Introduce new database models for conversation sessions, messages, and artifacts to support conversation history tracking.
- Implement API routes for listing conversations and retrieving detailed conversation data, enhancing user interaction with historical records.
- Add a conversation recorder service to persist conversation messages in real-time without disrupting ongoing calls.
- Update the frontend to display conversation history, including filtering and sorting options, improving user experience.
- Enhance the pipeline to integrate conversation history recording seamlessly during interactions.

backend/app.py

@@ -23,6 +23,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from routes import (
     assistants,
     auth,
+    conversations,
     health,
     knowledge_bases,
     model_registry,
@@ -52,6 +53,7 @@ app.add_middleware(
 
 app.include_router(health.router)
 app.include_router(auth.router)
+app.include_router(conversations.router)
 app.include_router(assistants.router)
 app.include_router(knowledge_bases.router)
 app.include_router(model_registry.router)