- Introduce the `check_duplicate_ids` function in `dataset.py` and
`doc.py` to check for and handle duplicate IDs.
- Update the deletion operation to ensure that when deleting datasets
and documents, error messages regarding duplicate IDs can be returned.
- Implement the `check_duplicate_ids` function in `api_utils.py` to
return unique IDs and error messages for duplicate IDs.


### What problem does this PR solve?

Close https://github.com/infiniflow/ragflow/issues/6234

### Type of change

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

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Co-authored-by: wenju.li <wenju.li@deepctr.cn>
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>