Add Pseudonymize option to GUI

[rahul-p19]

Closes #14118

To add the button in the GUI, I updated MainMenu and StandardActions to include Pseudonymize Library option. I created a new PseudonymizeAction class extending SimpleCommand - on clicking the button, execute() runs and uses the existing Pseudonymize class to pseudonymize the current library, then exports the result to .pseudo.bib and .pseudo.csv (keys) files.

Steps to test

Load a .bib file or library into JabRef, then go to the "Tools" menu in the Main Menu Bar at the top. Click on Pseudonymize Library. Choose a directory using the dialog and then the files are downloaded. In case there already exists a file with the same name at the same directory, the user is asked if they'd like to override the file or cancel the operation.

Screenshot

Screen Recording

Screen.Recording.2025-12-13.at.12.32.03.AM.mov

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.

[github-actions]

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[subhramit]

Hey, your changes look promising. Please run openrewrite as instructed by @jabref-machine

[calixtus]

Please use the ellipsis in the localization too. In other languages there might be different ways to indicate this. See NEW_LIBRARY_FROM_PDF_OFFLINE.
Yes, i know, there are still other commands who do it like you did, but these need to be addressed in another PR.

[subhramit]

One minor comment

[subhramit]

I am aware that .pseudo exists in the cli tool, but can you change this to _pseudo instead here?

[subhramit]

Lgtm