File Upload/Download Bug Fixer

Help me debug file upload/download issues in my application.

**Operation:** {{OPERATION}}
**Framework:** {{FRAMEWORK}}

**Frontend code:**
```{{FRONTEND_LANGUAGE}}
{{FRONTEND_CODE}}
```

**Backend code:**
```{{BACKEND_LANGUAGE}}
{{BACKEND_CODE}}
```

**File type:** {{FILE_TYPE}}
**File size:** {{FILE_SIZE}}
**Error:**
```
{{ERROR}}
```

**Expected behavior:** {{EXPECTED}}

Please provide:
1. **Request Analysis**: Check multipart/form-data handling
2. **Size Limits**: Verify file size configurations
3. **Stream Handling**: Check streaming for large files
4. **Headers Check**: Verify Content-Type and Content-Disposition
5. **Fixed Code**: Corrected upload/download code
6. **Progress Tracking**: Implement progress indicators
7. **Error Handling**: Proper error handling for file ops
8. **Security Check**: Validate file types and sanitize