actually just move the language types, don't use the one from the common assembly

Dalamud/Utility/ClientLanguageExtensions.cs

@@ -0,0 +1,26 @@
+using Dalamud.Game;
+
+namespace Dalamud.Utility;
+
+/// <summary>
+/// Extension methods for the <see cref="ClientLanguage"/> class.
+/// </summary>
+public static class ClientLanguageExtensions
+{
+    /// <summary>
+    /// Converts a Dalamud ClientLanguage to the corresponding Lumina variant.
+    /// </summary>
+    /// <param name="language">Language to convert.</param>
+    /// <returns>Converted language.</returns>
+    public static Lumina.Data.Language ToLumina(this ClientLanguage language)
+    {
+        return language switch
+        {
+            ClientLanguage.Japanese => Lumina.Data.Language.Japanese,
+            ClientLanguage.English => Lumina.Data.Language.English,
+            ClientLanguage.German => Lumina.Data.Language.German,
+            ClientLanguage.French => Lumina.Data.Language.French,
+            _ => throw new ArgumentOutOfRangeException(nameof(language)),
+        };
+    }
+}