新增搜索标题和网页标题双字段

- 数据库新增 search_title 字段存储搜索结果标题
- product_names 存储抓取到的网页标题
- 搜索页面显示两个标题（搜索标题 + 网页标题）
- 内容库页面也显示两个标题

services/search_service.py

@@ -390,9 +390,9 @@ class SearchService:
         
         return results
     
-    def save_to_articles(self, product_names, category, keywords, summary, content, source, url=None):
+    def save_to_articles(self, product_names, category, keywords, summary, content, source, url=None, search_title=None):
         """保存搜索结果到内容库"""
-        return db.add_article(product_names, category, keywords, summary, content, source, url)
+        return db.add_article(product_names, category, keywords, summary, content, source, url, search_title)
 
 # 全局搜索服务实例
 search_service = SearchService()