Bundling R alone was not enough: R links libicuuc, and Arch moves ICU
regularly. The obvious fix - pinning 'icu>=78 <79' in depends - is worse
than the disease on a rolling distro, because pacman would then refuse to
upgrade ICU while JASP is installed, blocking the user's whole system
upgrade until a rebuild lands.
So bundle-libs.sh copies every non-system shared library into
/opt/jasp-desktop/lib and rewrites rpaths, by denylist rather than
allowlist. depends now carries no version constraints at all.
Qt6 stays system-provided on purpose - Qt is binary compatible across Qt 6
minors, and bundling QtWebEngine would add ~500 MB. That also means the
only rebuild triggers left are a new JASP release and a Qt major bump;
rebuilding for anything else would cost users a 1.7 GB re-download.
Also fixes check-upstream.py querying only repo=Extra, which silently
returned nothing for icu (it lives in core).
