fix(home): move gtk3 to home.packages for FreeCAD GSettings schema

FreeCAD is a home-manager package, so its GSettings schema dependency
(org.gtk.Settings.FileChooser) must also be in home.packages for
home-manager to include it in XDG_DATA_DIRS. Having gtk3 only in
system packages left it invisible to the user session.

configuration.nix

@@ -103,7 +103,6 @@
     cacert
     code-cursor
     adwaita-icon-theme
-    gtk3  # Provides org.gtk.Settings.FileChooser schema for FreeCAD
     pkgs-unstable.claude-code  # Use unstable for latest version
     yubikey-manager
   ];

home.nix

@@ -28,6 +28,7 @@
     gnomeExtensions.just-perfection
     gnomeExtensions.arc-menu
     freecad
+    gtk3  # Provides org.gtk.Settings.FileChooser schema for FreeCAD
   ];
 
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