fix(wallpaper): repaint monitors hotplugged after login

awww-daemon paints only the outputs present when `awww img` last ran and does
not repaint a monitor connected later, so it comes up on the daemon's black
fill — which a transparent foot then shows instead of the wallpaper. Add
`wallpaper-hotplug`: it watches Hyprland's event socket and re-runs `setbg`
(which pushes to all outputs) on each `monitoradded`.

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

modules/home.nix

@@ -614,6 +614,8 @@ 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"
       ];
     };
   };