add input method to thinkpad

hosts/nixos/thinkpad/system.nix

@@ -157,6 +157,15 @@ in
     options = "";
   };
 
+  # Input method configuration
+  i18n.inputMethod = {
+    enabled = "ibus";
+    ibus.engines = with pkgs.ibus-engines; [
+      libpinyin  # Chinese Simplified Pinyin
+      mozc       # Japanese (Romaji)
+    ];
+  };
+
   # Exclude unwanted GNOME default packages
   environment.gnome.excludePackages = with pkgs; [
     gnome-tour

modules/gnome.nix

@@ -32,9 +32,13 @@ in
         picture-options = "scaled";
       };
 
-      # Input sources - US English
+      # Input sources - US English, Chinese Pinyin, Japanese
       "org/gnome/desktop/input-sources" = {
-        sources = [ (mkTuple [ "xkb" "us" ]) ];
+        sources = [
+          (mkTuple [ "xkb" "us" ])
+          (mkTuple [ "ibus" "libpinyin" ])
+          (mkTuple [ "ibus" "mozc-jp" ])
+        ];
         xkb-options = [ "" ];
       };