Refresh after pacman transactions and local repo builds

Add a pacman hook that runs update-notify for each logged-in user with the timer active, and a path unit that users can point at their local repo databases to refresh after aur build.

update-notify-refresh

@@ -0,0 +1,10 @@
+#!/bin/bash
+# Run update-notify for every logged-in user whose timer is active (called by the pacman hook as root)
+systemctl list-units --plain --no-legend --state=running 'user@*.service' |
+while read -r unit _; do
+    uid=${unit#user@}
+    uid=${uid%.service}
+    user=$(id -nu "$uid") || continue
+    systemctl --user -M "$user@" is-active --quiet update-notify.timer || continue
+    systemctl --user -M "$user@" start --no-block update-notify.service
+done