Add lib.optionals pkgs.stdenv.isLinux guards to roles that contain
Linux-only packages or services to prevent build failures on Darwin:
- communication: Guard Electron apps (element-desktop, fluffychat,
nextcloud-talk-desktop) that don't build on Darwin due to electron
build-from-source limitations
- kdeconnect: Guard entire config block since services.kdeconnect
requires D-Bus and systemd (Linux-only)
- sync: Guard syncthingtray package (requires Linux system tray)
- email: Guard systemd.user.services/timers (Darwin uses launchd)
- desktop: Guard Linux-only packages, services, and KDE-specific
configurations including gnome-keyring, systemd services, and
XDG mime associations
Implements bead: nixos-configs-tcu
John Ogle
b9f56ff57d