### What problem does this PR solve?

Fix errors detected by Ruff

### Type of change

- [x] Refactoring

https://github.com/infiniflow/ragflow/issues/2496

### 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

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [x] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

### What problem does this PR solve?


### Type of change

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

### What problem does this PR solve?

Let file in knowledgebases visible in file manager.
#162 

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

### What problem does this PR solve?


### Type of change

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

### What problem does this PR solve?

### Type of change

- [x] Documentation Update