Implement knowledge base management and enhance assistant configuration

Add CRUD functionality for knowledge bases, including routes for listing, creating, updating, and deleting knowledge bases. Update the assistant model to include foreign key references to knowledge bases and modify the assistant configuration to handle external API keys securely. Refactor related services and routes to accommodate these changes, ensuring proper handling of credential resolution and configuration normalization.

backend/app.py

@@ -18,7 +18,14 @@ from db.session import init_db
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
-from routes import assistants, credentials, health, voice_webrtc, voice_ws
+from routes import (
+    assistants,
+    credentials,
+    health,
+    knowledge_bases,
+    voice_webrtc,
+    voice_ws,
+)
 
 
 @asynccontextmanager
@@ -40,6 +47,7 @@ app.add_middleware(
 app.include_router(health.router)
 app.include_router(assistants.router)
 app.include_router(credentials.router)
+app.include_router(knowledge_bases.router)
 app.include_router(voice_webrtc.router)
 app.include_router(voice_ws.router)