Fix trailing slash issue in chat endpoint (405 Method Not Allowed)

backend/app/api/chat.py

@@ -11,7 +11,7 @@ from ..services.metrics_logger import (
 router = APIRouter()
 
 
-@router.post("/", response_model=ChatResponse, summary="Chat using generated system prompt")
+@router.post("", response_model=ChatResponse, summary="Chat using generated system prompt")
 async def chat(req: ChatRequest):
     if not req.system_prompt:
         raise HTTPException(status_code=400, detail="system_prompt is required")