chore: deprecate standalone SecureStoreManager utility

Move SecureStoreManager project and tests to Deprecated folder and remove
from solution. SecureStore functionality is now integrated into ConfigManager.

Deprecated/JdeScoping.SecureStoreManager/Program.cs

@@ -0,0 +1,22 @@
+using Avalonia;
+
+namespace JdeScoping.SecureStoreManager;
+
+internal class Program
+{
+    /// <summary>
+    /// The main entry point for the application.
+    /// </summary>
+    /// <param name="args">Command-line arguments.</param>
+    [STAThread]
+    public static void Main(string[] args) => BuildAvaloniaApp()
+        .StartWithClassicDesktopLifetime(args);
+
+    /// <summary>
+    /// Builds the Avalonia application configuration.
+    /// </summary>
+    public static AppBuilder BuildAvaloniaApp()
+        => AppBuilder.Configure<App>()
+            .UsePlatformDetect()
+            .LogToTrace();
+}