feat: manage wlsunset via systemd user service

Move nightlight from niri spawn-at-startup to a systemd user service
with After=kanshi.service to ensure all outputs are configured before
wlsunset starts. Toggle now uses enable/disable --now for persistent
state across reboots.

scripts/moonarch-doctor

@@ -178,7 +178,7 @@ section "User Services"
 if [[ $EUID -eq 0 ]]; then
     warn "Running as root — skipping user service checks"
 else
-    for svc in kanshi stasis cliphist-text cliphist-image; do
+    for svc in kanshi wlsunset stasis cliphist-text cliphist-image; do
         check_user_service "$svc"
     done
 fi

scripts/post-install.sh

@@ -124,6 +124,7 @@ fi
 log "Enabling systemd user services..."
 USER_SERVICES=(
     "kanshi"
+    "wlsunset"
     "stasis"
     "cliphist-text"
     "cliphist-image"

scripts/transform.sh

@@ -345,6 +345,7 @@ echo "source /etc/zsh/zshrc.moonarch" >> "$HOME/.zshrc"
 log "Enabling systemd user services..."
 USER_SERVICES=(
     "kanshi"
+    "wlsunset"
     "stasis"
     "cliphist-text"
     "cliphist-image"