refactor(copyparty): separate deployment and service policy

Move Copyparty rendering into shared dotfiles utilities, keep guest wiring focused on host/container plumbing, and let the service module derive effective volume policy.

src/dotfiles/default.nix

@@ -14,7 +14,7 @@ let
     registry = registry.collected;
   };
 
-  util = import ./util.nix { inherit lib; };
+  util = import ./util { inherit lib; };
 
   registry = import ./registry.nix {
     inherit lib util;