feat: add wlsunset nightlight toggle with Waybar module

Add blue light filter support via wlsunset, toggleable through a Waybar
module in the brightness group. Nightlight icon is the primary element,
backlight slider expands on click.

- Add wlsunset package to official.txt
- Add moonarch-nightlight toggle script (kill/restart wlsunset)
- Add moonarch-waybar-nightlight status script (JSON output)
- Add custom/nightlight module to group/brightness in Waybar config
- Add Catppuccin Yellow highlight for active nightlight state
- Add wlsunset autostart in Niri config (5000K night temperature)

defaults/xdg/niri/config.kdl

@@ -86,6 +86,7 @@ spawn-at-startup "nm-applet" "--indicator"
 spawn-sh-at-startup "waypaper --restore"
 // spawn-sh-at-startup "nemo . &> /dev/null &"
 spawn-sh-at-startup "foot --server"
+spawn-at-startup "wlsunset" "-T" "6500" "-t" "5000" "-S" "00:00" "-s" "00:01"
 // Clipboard history managed by cliphist.service (systemd user service)
 
 hotkey-overlay {