phone: Move gtk config to gtk module

This is part of simplifying the phone module to make it as consistent
with the rest of the home-manager environment as possible.

home/gtk.nix

@@ -1,5 +1,15 @@
-{ pkgs, ... }:
+{
+  nix-config,
+  config,
+  pkgs,
+  ...
+}:
 
+let
+  phosh-backgrounds = nix-config.packages.${pkgs.system}.phosh-backgrounds.override {
+    color = config.lib.stylix.colors.base00;
+  };
+in
 {
   gtk = {
     enable = true;
@@ -18,4 +28,28 @@
       name = "Fluent-dark";
     };
   };
+
+  stylix.targets.gtk.extraCss = # css
+    ''
+      phosh-lockscreen {
+        background: url('${phosh-backgrounds}/wall-lock.jpg');
+      }
+
+      phosh-app-grid {
+        background: url('${phosh-backgrounds}/wall-grid.jpg');
+      }
+
+      phosh-top-panel {
+        background: url('${phosh-backgrounds}/wall-panel.jpg');
+      }
+
+      phosh-home {
+        background: url('${phosh-backgrounds}/wall-home.jpg');
+      }
+
+      phosh-lockscreen, phosh-app-grid, phosh-top-panel, phosh-home {
+        background-size: cover;
+        background-position: center;
+      }
+    '';
 }

hosts/phone/configuration.nix

@@ -12,10 +12,6 @@ let
   inherit (config.modules.system) username;
   inherit (builtins) attrValues;
 
-  phosh-backgrounds = self.packages.${pkgs.system}.phosh-backgrounds.override {
-    color = config.lib.stylix.colors.base00;
-  };
-
   no = {
     name = "";
     settings = {
@@ -169,32 +165,6 @@ in
         };
       };
     };
-
-    background = {
-      stylix.targets.gtk.extraCss = # css
-        ''
-          phosh-lockscreen {
-            background: url('${phosh-backgrounds}/wall-lock.jpg');
-          }
-
-          phosh-app-grid {
-            background: url('${phosh-backgrounds}/wall-grid.jpg');
-          }
-
-          phosh-top-panel {
-            background: url('${phosh-backgrounds}/wall-panel.jpg');
-          }
-
-          phosh-home {
-            background: url('${phosh-backgrounds}/wall-home.jpg');
-          }
-
-          phosh-lockscreen, phosh-app-grid, phosh-top-panel, phosh-home {
-            background-size: cover;
-            background-position: center;
-          }
-        '';
-    };
   };
 
   environment = {