feat: soften quota messaging

ai_knowledge_base_v2/apps/backend/app/services/chat_service.py

@@ -226,7 +226,10 @@ class ChatService:
     @staticmethod
     def _ensure_quota(user: User) -> None:
         if user.daily_chat_used >= user.daily_chat_limit:
-            raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="今日提问次数已用完")
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail="今天的陪伴对话已经比较多了，建议先消化当前回答和功课；如需继续使用，可以联系运营老师确认权益。",
+            )
 
     @staticmethod
     def _ensure_topic_quota(db: Session, user: User, session: ChatSession, entitlement) -> None: