Fix dunst config loading, modernize notification handling

- Point dunst to /etc/xdg/dunst/dunstrc via -conf flag (dunst with
  SYSCONFDIR=/etc does not search XDG_CONFIG_DIRS)
- Update dunstrc: fix legacy offset syntax, replace missing
  Tela-purple-dark icon theme with Colloid-Grey-Catppuccin-Dark
- Replace dunstify with notify-send in moonarch-cpugov for
  daemon-agnostic notifications, fix broken icon path
- Replace dbus-monitor based moonarch-dnd script with inline
  waybar polling (interval 2s), fixing process accumulation bug
- Add #custom-dnd to waybar CSS padding rule

defaults/xdg/waybar/config

@@ -228,11 +228,10 @@
         "on-click": "alacritty paru"
     },
     "custom/dnd": {
-        "format": " {} ",
-        "exec": "moonarch-dnd",
-        "return-type": "json",
-        "on-click": "dunstctl set-paused toggle",
-        "restart-interval": 1,
+        "format": "{}",
+        "exec": "dunstctl is-paused | sed 's/false/󰂚/;s/true/󰂛/'",
+        "interval": 2,
+        "on-click": "dunstctl set-paused toggle"
     },
     "custom/notification": {
         "tooltip": false,