feat(moonarch-git): package battery conservation mode assets

Add udev rule and systemd service to PKGBUILD. Create /var/lib/moonarch
state directory and enable batsaver restore service on laptops in the
post-install hook.

moonarch-git/PKGBUILD

@@ -190,6 +190,14 @@ package() {
             "$pkgdir/etc/systemd/user/graphical-session.target.wants/$(basename "$svc")"
     done
 
+    # --- udev rules -> /usr/lib/udev/rules.d/ ---
+    install -Dm644 defaults/etc/udev/rules.d/90-moonarch-battery.rules \
+        "$pkgdir/usr/lib/udev/rules.d/90-moonarch-battery.rules"
+
+    # --- Systemd system service (battery conservation restore) -> /usr/lib/systemd/system/ ---
+    install -Dm644 defaults/etc/systemd/system/moonarch-batsaver.service \
+        "$pkgdir/usr/lib/systemd/system/moonarch-batsaver.service"
+
 }
 
 backup=(