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/bin/moonarch-nightlight

@@ -0,0 +1,12 @@
+#!/bin/bash
+# ABOUTME: Toggles wlsunset night light on/off.
+# ABOUTME: Kills or restarts wlsunset process, signals waybar for refresh.
+
+if pgrep -x wlsunset > /dev/null; then
+    pkill -x wlsunset
+else
+    wlsunset -T 6500 -t 5000 -S 00:00 -s 00:01 &
+    disown
+fi
+
+pkill -RTMIN+11 waybar

defaults/bin/moonarch-waybar-nightlight

@@ -0,0 +1,9 @@
+#!/bin/bash
+# ABOUTME: Outputs JSON status for waybar nightlight module.
+# ABOUTME: Shows warm icon when wlsunset is active, cool icon when off.
+
+if pgrep -x wlsunset > /dev/null; then
+    jq -nc '{text: "󰌵", alt: "on", tooltip: "Nightlight: An (5000K)", class: "on"}'
+else
+    jq -nc '{text: "󰌶", alt: "off", tooltip: "Nightlight: Aus", class: "off"}'
+fi

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 {

defaults/xdg/waybar/config

@@ -61,6 +61,7 @@
     "group/brightness": {
         "orientation": "inherit",
         "modules": [
+            "custom/nightlight",
             "backlight",
             "backlight/slider"
         ],
@@ -304,6 +305,14 @@
             "<span color='#dd532e' size='8pt' rise='1.5pt'>█</span>"
         ]
     },
+    "custom/nightlight": {
+        "exec": "moonarch-waybar-nightlight",
+        "return-type": "json",
+        "interval": "once",
+        "signal": 11,
+        "on-click": "moonarch-nightlight",
+        "format": "{}"
+    },
     "custom/cpugov": {
         "exec": "moonarch-waybar-cpugov",
         "return-type": "json",

defaults/xdg/waybar/style.css

@@ -257,6 +257,10 @@ widget widget>* {
     color: alpha(@theme_selected_bg_color, 0.9);
 }
 
+#custom-nightlight.on {
+    color: #f9e2af;
+}
+
 menu {
     border-radius: 4px;
 }