Web: Fixed the download and preview file not authorized. (#3652)

https://github.com/infiniflow/ragflow/issues/3651

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

api/apps/file_app.py

@@ -323,7 +323,7 @@ def rename():
 
 
 @manager.route('/get/<file_id>', methods=['GET'])
-# @login_required
+@login_required
 def get(file_id):
     try:
         e, file = FileService.get_by_id(file_id)