refactor: group stow packages into common, mac and kde

Split the packages by platform so each app stays an opt-in Stow package
under common/, mac/ or kde/. KDE gets its own Fastfetch, Helium and
Spectacle packages, and darwin-breeze becomes kde/theme. The READMEs
document stowing a whole group as well as individual packages.

kde/tray-icons/.local/share/ngosen-breeze-icons/restart-fcitx5.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+# Restart fcitx5 through KWin (KDE Wayland) so it keeps the Wayland input method frontend.
+L=$(kreadconfig6 --file kwinrc --group Wayland --key InputMethod)
+[[ -n $L ]] || L=/usr/share/applications/fcitx5-wayland-launcher.desktop
+pkill -x fcitx5; sleep 1
+kwriteconfig6 --notify --file kwinrc --group Wayland --key InputMethod --delete; sleep 1
+kwriteconfig6 --notify --file kwinrc --group Wayland --key InputMethod "$L"