gtk fixes to ensure no border radii etc

modules/home/services/gtk/default.nix

@@ -56,7 +56,8 @@ in {
         '';
       };
 
-      gtk3.extraConfig = {
+      gtk3 = {
+        extraConfig = {
           # Lets be easy on the eyes. This should be easy to make dependent on
           # the "variant" of the theme, but I never use a light theme anyway.
           gtk-application-prefer-dark-theme = true;
@@ -78,8 +79,13 @@ in {
           gtk-xft-hinting = 1;
           gtk-xft-hintstyle = "hintslight";
         };
+        extraCss = ''
+          window { border-radius: 0; }
+        '';
+      };
 
-      gtk4.extraConfig = {
+      gtk4 = {
+        extraConfig = {
           # Prefer dark theme.
           gtk-application-prefer-dark-theme = true;
 
@@ -96,6 +102,10 @@ in {
           gtk-xft-hinting = 1;
           gtk-xft-hintstyle = "hintslight";
         };
+        extraCss = ''
+          window { border-radius: 0; }
+        '';
+      };
     };
   };
 }