feat(api-server): add type hints

Author: NicholasGoh

backend/api/routers/llms.py

@@ -1,17 +1,22 @@
+from typing import AsyncGenerator
+
 from fastapi import APIRouter
 from sse_starlette.sse import EventSourceResponse
+from starlette.responses import Response
 
 from api.dependencies import LLMDep
 
 router = APIRouter(tags=["chat"])
 
 
-async def stream(query: str, llm: LLMDep):
+async def stream(
+    query: str, llm: LLMDep
+) -> AsyncGenerator[dict[str, str], None]:
     async for chunk in llm.astream_events(query):
         yield dict(data=chunk)
 
 
 @router.get("/chat/completions")
-async def completions(query: str, llm: LLMDep):
+async def completions(query: str, llm: LLMDep) -> Response:
     """Stream completions via Server Sent Events"""
     return EventSourceResponse(stream(query, llm))