feat(themes): declaratively manage icons, cursors, and dark/light modes

- Automatically detect light mode via 'light.mode' file in theme folder
- Read icon theme name from 'icons.theme' file in theme folder
- Switch Stylix polarity and iconTheme based on theme selection
- Add yaru-theme and bibata-cursors to default packages
- Remove obsolete imperative nomarchy-theme-set-gnome script

bin/nomarchy-theme-set-gnome

@@ -1,18 +0,0 @@
-#!/bin/bash
-
-# Change gnome modes
-if [[ -f ~/.config/nomarchy/current/theme/light.mode ]]; then
-  gsettings set org.gnome.desktop.interface color-scheme "prefer-light"
-  gsettings set org.gnome.desktop.interface gtk-theme "Adwaita"
-else
-  gsettings set org.gnome.desktop.interface color-scheme "prefer-dark"
-  gsettings set org.gnome.desktop.interface gtk-theme "Adwaita-dark"
-fi
-
-# Change gnome icon theme color
-GNOME_ICONS_THEME=~/.config/nomarchy/current/theme/icons.theme
-if [[ -f $GNOME_ICONS_THEME ]]; then
-  gsettings set org.gnome.desktop.interface icon-theme "$(<$GNOME_ICONS_THEME)"
-else
-  gsettings set org.gnome.desktop.interface icon-theme "Yaru-blue"
-fi