sway: replace swaylock with gtklock, Star Wars theme lockscreen

Switch lockscreen from swaylock to gtklock. CSS styled with Star Wars
yellow (#FFE81F) on near-black background, cover-scaled wallpaper injected
at runtime via temp CSS to avoid path expansion issues in gtklock config.
Update sway background wallpaper to darth-vader-sam.jpg.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ansible/inventory/group_vars/desktop.yml

@@ -210,6 +210,10 @@ desktop_sway_dotfiles:
     src: .config/foot/
     dest: .config/foot/
     mode: preserve
+  - name: gtklock config
+    src: .config/gtklock/
+    dest: .config/gtklock/
+    mode: preserve
 
 desktop_flatpak_packages:
   - be.alexandervanhee.gradia