fix: include file size in existing file retrieval logic

Author: liuruibin

apps/knowledge/models/knowledge.py

@@ -350,6 +350,7 @@ def save(self, bytea=None, force_insert=False, force_update=False, using=None, u
         existing_file = QuerySet(File).filter(sha256_hash=sha256_hash).first()
         if existing_file:
             self.loid = existing_file.loid
+            self.file_size = existing_file.file_size
             return super().save()
 
         compressed_data = self._compress_data(bytea)