fix(SearchChain): with 关闭线程池

- 使用 with 语句管理 ThreadPoolExecutor，确保线程池正确关闭

app/chain/search.py

@@ -329,8 +329,10 @@ class SearchChain(ChainBase):
         self.progress.update(value=0,
                              text=f"开始搜索，共 {total_num} 个站点 ...",
                              key=ProgressKey.Search)
+        # 结果集
+        results = []
         # 多线程
-        executor = ThreadPoolExecutor(max_workers=len(indexer_sites))
+        with ThreadPoolExecutor(max_workers=len(indexer_sites)) as executor:
             all_task = []
             for site in indexer_sites:
                 if area == "imdbid":
@@ -346,8 +348,6 @@ class SearchChain(ChainBase):
                                            mtype=mediainfo.type if mediainfo else None,
                                            page=page)
                 all_task.append(task)
-        # 结果集
-        results = []
             for future in as_completed(all_task):
                 if global_vars.is_system_stopped:
                     break