Update comments (#4569)

### What problem does this PR solve?

Add license statement.

### Type of change

- [x] Refactoring

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

rag/app/paper.py

@@ -1,3 +1,6 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
 #  Licensed under the Apache License, Version 2.0 (the "License");
 #  you may not use this file except in compliance with the License.
 #  You may obtain a copy of the License at
@@ -10,6 +13,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 #
+
 import logging
 import copy
 import re