Added color themes (dark & light) (#148)

app/MindWork AI Studio/Settings/SettingsManager.cs

@@ -21,7 +21,7 @@ public sealed class SettingsManager(ILogger<SettingsManager> logger)
         Converters = { new JsonStringEnumConverter() },
     };
 
-    private ILogger<SettingsManager> logger = logger;
+    private readonly ILogger<SettingsManager> logger = logger;
     
     /// <summary>
     /// The directory where the configuration files are stored.
@@ -33,6 +33,11 @@ public sealed class SettingsManager(ILogger<SettingsManager> logger)
     /// </summary>
     public static string? DataDirectory { get; set; }
 
+    /// <summary>
+    /// Whether the app is in dark mode.
+    /// </summary>
+    public bool IsDarkMode { get; set; }
+
     /// <summary>
     /// The configuration data.
     /// </summary>