The reverse-DNS app ID should reflect a domain we actually control.
Renames the desktop file, AppStream metainfo, icon, Flatpak manifest,
and macOS bundle identifier from io.orbithub.OrbitHub to
org.darksingularity.OrbitHub. Also fixes a stale homepage URL in the
metainfo file pointing at an old git host.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
