Support field "arxiv" at eprint cleanup

[koppor]

Adds suport for moving arXiv ids when parsing with LLM.

Also follow-up to #13020: Fixes localization in NewEntry dialog

Steps to test

1. Parse E. G. Santana Jr., G. Benjamin, M. Araujo, and H. Santos, "Which Prompting Technique Should I Use? An Empirical Investigation of Prompting Techniques for Software Engineering Tasks", arXiv:2506.05614, Jun. 2025. with new entry dialog and LLM
2. See that arXiV id is written into eprint field

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• I manually tested my changes in running JabRef (always required)
• I added JUnit tests for changes (if applicable)
• [/] I added screenshots in the PR description (if change is visible to the user)
• I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• [/] I checked the user documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.