Breaking changes:
- App ID renamed from ink.whis.desktop to ink.whis.Whis
  (Flathub requires IDs not ending in .desktop)

Improvements:
- Use arboard wayland-data-control feature for clipboard
  (removes need for flatpak-spawn permission)
- Simplified clipboard code
- Updated all references to new app ID

This prepares the desktop app for Flathub submission.