Add MockSettingsManager for design mode without IO

StabilityMatrix.Avalonia/DesignData/DesignData.cs

@@ -17,7 +17,7 @@ public static class DesignData
 {
     static DesignData()
     {
-        var settingsManager = new SettingsManager
+        var settingsManager = new MockSettingsManager
         {
             Settings =
             {

StabilityMatrix.Avalonia/DesignData/MockSettingsManager.cs

@@ -0,0 +1,9 @@
+using StabilityMatrix.Core.Services;
+
+namespace StabilityMatrix.Avalonia.DesignData;
+
+public class MockSettingsManager : SettingsManager
+{
+    protected override void LoadSettings() {}
+    protected override void SaveSettings() {}
+}

StabilityMatrix.Core/Services/SettingsManager.cs

@@ -423,7 +423,7 @@ public class SettingsManager : ISettingsManager
     /// Loads settings from the settings file
     /// If the settings file does not exist, it will be created with default values
     /// </summary>
-    private void LoadSettings()
+    protected virtual void LoadSettings()
     {
         FileLock.EnterReadLock();
         try
@@ -451,7 +451,7 @@ public class SettingsManager : ISettingsManager
         }
     }
 
-    private void SaveSettings()
+    protected virtual void SaveSettings()
     {
         FileLock.TryEnterWriteLock(100000);
         try