remove data_manager.py and dfs.py

csst_common/dfs.py

-"""
-Identifier:     csst_common/dfs.py
-Name:           dfs.py
-Description:    DFS wrapper
-Author:         Bo Zhang
-Created:        2023-07-08
-Modified-History:
-    2023-07-08, Bo Zhang, implemented DFS
-    2023-07-11, Bo Zhang, updated DFS
-    2023-12-08, Bo Zhang, tweaks
-    2023-12-20, Bo Zhang, do nothing in DFS.__init__()
-    2023-12-28, Bo Zhang, add DFS.rec_to_table and DFS.rec_to_dlist
-    2025-01-02, Bo Zhang, use csst_dfs_client
-"""
-
-from astropy.table import Table
-from csst_dfs_client import (
-    level0,
-    level1,
-    catalog,
-    plan,
-)
-
-# from csst_dfs_api.common.catalog import CatalogApi
-# from csst_dfs_api.facility import (
-#     Level0DataApi,
-#     Level0PrcApi,
-#     Level1DataApi,
-#     Level1PrcApi,
-#     Level2DataApi,
-#     Level2TypeApi,
-#     OtherDataApi,
-# )
-
-
-class DFS:
-    def __init__(self):
-        self.level0 = level0
-        self.level1 = level1
-        self.catalog = catalog
-        self.plan = plan