feat(gui): regreet csd and background image

faucet/gui/greetd.nix

@@ -4,7 +4,14 @@
 , ... }: with lib; let
   cfg = config.faucet.gui;
 in mkIf (cfg.enable && cfg.session) {
-  programs.regreet.enable = true;
+  programs.regreet = {
+    enable = true;
+    cageArgs = [ "-s" "-d" "-m" "last" ];
+    settings = {
+      background.path = ../../share/54345906_p0.jpg;
+      gtk.application_prefer_dark_theme = true;
+    };
+  };
 
   environment.persistence."/nix/persist/fhs".directories = [ "/var/cache/regreet" ];
 }