Promoted from DIYStickyNotes/lib/ReleaseUpdater (byte-identical src) into a
reusable Gitea library. Adds LICENSE, .gitignore, library.properties,
keywords.txt and carries the ReleaseUpdaterCore native unit test for
downstream reuse.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
