Enhance Sway/Noctalia integration and align desktop docs

- Add canonical usb-drive-manager plugin to Noctalia (symlink from official)
- Remove nm-applet and blueman packages from nymph Sway session
- Run udiskie without tray (backend for automount/LUKS, UI via usb-drive-manager)
- Add screenOverrides support to Noctalia bar via inventory variables
- Add host_packages_absent task to packages_void role
- Update desktop docs with full plugin list and config layering
- Add focused validation check for Sway/Noctalia bootstrap

dotfiles/desktop/.config/noctalia/plugins.json

@@ -18,6 +18,10 @@
         "screenshot": {
             "enabled": true,
             "sourceUrl": "https://github.com/noctalia-dev/noctalia-plugins"
+        },
+        "usb-drive-manager": {
+            "enabled": true,
+            "sourceUrl": "https://github.com/noctalia-dev/noctalia-plugins"
         }
     },
     "version": 2