rename package from windsurf to devin-desktop

Update pkgname, pkgdesc, url, license, source paths, binary names,
and script references to reflect the upstream rebranding. Add
conflicts=('windsurf') and provides=('windsurf' 'devin-desktop') for
clean AUR upgrades from the old package.

Generated with [Devin](https://cli.devin.ai/docs)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

cleanup.sh

@@ -1,5 +1,5 @@
 rm -f .SRCINFO
 rm -f code.sh
-rm -f windsurf*.tar.zst
-rm -f windsurf*.deb
+rm -f devin-desktop*.tar.zst
+rm -f devin-desktop*.deb
 rm -rf src