fix(home): keep waybar + wallpaper on surviving monitor after unplug

Hyprland drops the layer-shell surfaces on the remaining output when a
monitor is removed and does not recreate them, so waybar and the awww
wallpaper vanish on unplug. The socket2 watcher only reacted to
`monitoradded`, which masked it — reconnecting re-fired the add and
restored both. Handle `monitorremoved` too, and on either event re-push
the wallpaper and reload waybar (SIGUSR2 rebuilds its per-output bars).
Renamed `wallpaper-hotplug` to `monitor-hotplug` since it now does both.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home.nix

@@ -661,8 +661,8 @@ in
         # the ~/.local/share/bg symlink if it exists.
         "awww-daemon"
         "sh -c '[ -e \"$HOME/.local/share/bg\" ] && awww img \"$HOME/.local/share/bg\"'"
-        # re-push the wallpaper onto monitors connected after login (media.nix)
-        "wallpaper-hotplug"
+        # re-push wallpaper + reload waybar on monitor add/remove (media.nix)
+        "monitor-hotplug"
       ];
     };
   };