fix(adminui): stale-open guards, validation summaries, key-delete confirm, error boundary (#604)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/AddReferenceModal.razor

@@ -80,11 +80,20 @@
     private string? _error;
     private bool _wasVisible;
 
+    // Bumped on every open and close so a superseded picker-root load can't install its tree under a
+    // different equipment's (or a re-opened) modal (RawBrowseModal idiom).
+    private int _openGeneration;
+
+    private bool IsStale(int generation) => generation != _openGeneration || !Visible;
+
     protected override async Task OnParametersSetAsync()
     {
         // Reset + reload only on the false→true transition so re-renders while open don't wipe state.
+        if (!Visible && _wasVisible) { _openGeneration++; }
         if (Visible && !_wasVisible)
         {
+            _wasVisible = true;
+            var generation = ++_openGeneration;
             _selected.Clear();
             _error = null;
             _roots = Array.Empty<RawNode>();
@@ -94,6 +103,7 @@
             var root = string.IsNullOrEmpty(EquipmentId)
                 ? null
                 : await Svc.LoadReferencePickerRootAsync(EquipmentId);
+            if (IsStale(generation)) { return; }
             _roots = root is null ? Array.Empty<RawNode>() : new[] { root };
             _loading = false;
         }