feat: config max_search_results for search engine (#192)

* feat: implement UI

* feat: config max_search_results for search engine via api

---------

Co-authored-by: Henry Li <henry1943@163.com>

src/server/chat_request.py

@@ -38,6 +38,9 @@ class ChatRequest(BaseModel):
     max_step_num: Optional[int] = Field(
         3, description="The maximum number of steps in a plan"
     )
+    max_search_results: Optional[int] = Field(
+        3, description="The maximum number of search results"
+    )
     auto_accepted_plan: Optional[bool] = Field(
         False, description="Whether to automatically accept the plan"
     )