docs: add XML documentation and ConfigManager implementation plans

Add comprehensive XML documentation (param/returns tags) across 132 source
files to improve IntelliSense and API discoverability. Include ConfigManager
design documents and implementation plans for phases 1-9.

NEW/src/Utils/JdeScoping.SecureStoreManager/Views/MainWindow.axaml.cs

@@ -9,6 +9,9 @@ public partial class MainWindow : Window
 {
     private MainWindowViewModel? ViewModel => DataContext as MainWindowViewModel;
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="MainWindow"/> class.
+    /// </summary>
     public MainWindow()
     {
         InitializeComponent();

NEW/src/Utils/JdeScoping.SecureStoreManager/Views/NewStoreDialog.axaml.cs

@@ -10,8 +10,14 @@ namespace JdeScoping.SecureStoreManager.Views;
 
 public partial class NewStoreDialog : Window
 {
+    /// <summary>
+    /// Gets the view model for this dialog.
+    /// </summary>
     public NewStoreDialogViewModel ViewModel => (NewStoreDialogViewModel)DataContext!;
 
+    /// <summary>
+    /// Initializes a new instance of the NewStoreDialog.
+    /// </summary>
     public NewStoreDialog()
     {
         InitializeComponent();

NEW/src/Utils/JdeScoping.SecureStoreManager/Views/OpenStoreDialog.axaml.cs

@@ -10,8 +10,14 @@ namespace JdeScoping.SecureStoreManager.Views;
 
 public partial class OpenStoreDialog : Window
 {
+    /// <summary>
+    /// Gets the view model for this dialog.
+    /// </summary>
     public OpenStoreDialogViewModel ViewModel => (OpenStoreDialogViewModel)DataContext!;
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="OpenStoreDialog"/> class.
+    /// </summary>
     public OpenStoreDialog()
     {
         InitializeComponent();

NEW/src/Utils/JdeScoping.SecureStoreManager/Views/SecretEditDialog.axaml.cs

@@ -8,14 +8,25 @@ namespace JdeScoping.SecureStoreManager.Views;
 
 public partial class SecretEditDialog : Window
 {
+    /// <summary>
+    /// Gets the view model for this dialog.
+    /// </summary>
     public SecretEditDialogViewModel ViewModel => (SecretEditDialogViewModel)DataContext!;
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SecretEditDialog"/> class for creating a new secret.
+    /// </summary>
     public SecretEditDialog()
     {
         InitializeComponent();
         DataContext = new SecretEditDialogViewModel();
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SecretEditDialog"/> class for editing an existing secret.
+    /// </summary>
+    /// <param name="key">The secret key.</param>
+    /// <param name="value">The secret value.</param>
     public SecretEditDialog(string key, string value)
     {
         InitializeComponent();