chore(jenkins): promote nfs plugin from ./alpha to primary entry point

[ciiay]

Hey, I just made a Pull Request!

BREAKING: The New Frontend System (NFS) plugin has been promoted from the ./alpha subpath to the primary . entry point. The legacy plugin has been moved to the new ./legacy subpath.

Migration steps:

• If you were importing from @backstage-community/plugin-jenkins/alpha to use the NFS plugin, update your imports to @backstage-community/plugin-jenkins.
• If you were importing from @backstage-community/plugin-jenkins (the legacy plugin), update your imports to @backstage-community/plugin-jenkins/legacy.

The ./alpha subpath has been removed because this plugin does not ship translations.

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)
• All your commits have a Signed-off-by line in the message. (more info)

Made with Cursor

[backstage-goalie]

Missing Changesets

The following package(s) are changed by this PR but do not have a changeset:

• @backstage-community/plugin-jenkins-backend

See CONTRIBUTING.md for more information about how to add changesets.

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@backstage-community/plugin-jenkins-backend	workspaces/jenkins/plugins/jenkins-backend	none	v0.30.0
@backstage-community/plugin-jenkins	workspaces/jenkins/plugins/jenkins	major	v0.33.0