Refactor web search plugin and clean up code

Refactored the web search plugin by removing the old Bing search implementation and reorganizing the plugin structure. Introduced modular search engine classes under 'web_search_tool/engines' and utility tools under 'web_search_tool/tools' and 'web_search_tool/utils'. Updated references and initialization logic to support multiple search engines and improved maintainability. Also performed minor code cleanups and replaced 'except ...: pass' with 'except ...: ...' for brevity.

src/chat/utils/chat_message_builder.py

@@ -786,9 +786,8 @@ def build_pic_mapping_info(pic_id_mapping: Dict[str, str]) -> str:
                 image = session.execute(select(Images).where(Images.image_id == pic_id)).scalar()
                 if image and image.description:
                     description = image.description
-        except Exception:
+        except Exception: ...
             # 如果查询失败，保持默认描述
-            pass
 
         mapping_lines.append(f"[{display_name}] 的内容：{description}")