feat: Add Instance Details ViewModel and UI for managing instance credentials

- Introduced InstanceDetailsViewModel to handle loading and displaying instance-specific credentials.
- Created InstanceDetailsWindow and associated XAML for displaying admin, database, and OAuth2 credentials.
- Updated InstancesViewModel to include command for opening instance details.
- Enhanced SettingsViewModel to manage Bitwarden and Xibo Bootstrap configurations, including connection testing.
- Added UI components for Bitwarden Secrets Manager and Xibo Bootstrap OAuth2 settings in the SettingsView.
- Implemented password visibility toggles and clipboard copy functionality for sensitive information.

OTSSignsOrchestrator.Desktop/Views/InstancesView.axaml.cs

@@ -1,11 +1,37 @@
 using Avalonia.Controls;
+using OTSSignsOrchestrator.Desktop.ViewModels;
 
 namespace OTSSignsOrchestrator.Desktop.Views;
 
 public partial class InstancesView : UserControl
 {
+    private InstancesViewModel? _vm;
+
     public InstancesView()
     {
         InitializeComponent();
+        DataContextChanged += OnDataContextChanged;
+    }
+
+    private void OnDataContextChanged(object? sender, EventArgs e)
+    {
+        if (_vm is not null)
+            _vm.OpenDetailsRequested -= OnOpenDetailsRequested;
+
+        _vm = DataContext as InstancesViewModel;
+
+        if (_vm is not null)
+            _vm.OpenDetailsRequested += OnOpenDetailsRequested;
+    }
+
+    private async void OnOpenDetailsRequested(InstanceDetailsViewModel detailsVm)
+    {
+        var window = new InstanceDetailsWindow { DataContext = detailsVm };
+        var owner  = TopLevel.GetTopLevel(this) as Window;
+        if (owner is not null)
+            await window.ShowDialog(owner);
+        else
+            window.Show();
     }
 }
+