feat(connection): implement refresh command for tree nodes

- Add RefreshAsync() to BucketNode to reload scopes
- Add RefreshAsync() to ScopeNode to reload collections
- Implement OnRefresh in ViewModel for ConnectionNode, BucketNode, ScopeNode
- Show "Refreshing..." indicator while reloading children

Author: CalvinAllen

src/CodingWithCalvin.CouchbaseExplorer/ViewModels/BucketNode.cs

@@ -34,6 +34,14 @@ protected override async void OnExpanded()
             await LoadScopesAsync();
         }
 
+        public async Task RefreshAsync()
+        {
+            _hasLoadedScopes = false;
+            Children.Clear();
+            Children.Add(new PlaceholderNode { Name = "Refreshing..." });
+            await LoadScopesAsync();
+        }
+
         public async Task LoadScopesAsync()
         {
             IsLoading = true;

src/CodingWithCalvin.CouchbaseExplorer/ViewModels/CouchbaseExplorerViewModel.cs

@@ -150,14 +150,32 @@ private async void OnConnectRequested(ConnectionNode connection)
             await ConnectToNodeAsync(connection);
         }
 
-        private void OnRefresh(object parameter)
+        private async void OnRefresh(object parameter)
         {
-            // TODO: Refresh selected node or all connections
+            var node = parameter as TreeNodeBase ?? SelectedNode;
+            if (node == null)
+            {
+                return;
+            }
+
+            switch (node)
+            {
+                case ConnectionNode connection when connection.IsConnected:
+                    await LoadBucketsAsync(connection);
+                    break;
+                case BucketNode bucket:
+                    await bucket.RefreshAsync();
+                    break;
+                case ScopeNode scope:
+                    await scope.RefreshAsync();
+                    break;
+            }
         }
 
         private bool CanRefresh(object parameter)
         {
-            return SelectedNode != null || Connections.Count > 0;
+            var node = parameter as TreeNodeBase ?? SelectedNode;
+            return node is ConnectionNode conn ? conn.IsConnected : node is BucketNode || node is ScopeNode;
         }
 
         private void OnCollapseAll(object parameter)

src/CodingWithCalvin.CouchbaseExplorer/ViewModels/ScopeNode.cs

@@ -30,6 +30,14 @@ protected override async void OnExpanded()
             await LoadCollectionsAsync();
         }
 
+        public async Task RefreshAsync()
+        {
+            _hasLoadedCollections = false;
+            Children.Clear();
+            Children.Add(new PlaceholderNode { Name = "Refreshing..." });
+            await LoadCollectionsAsync();
+        }
+
         public async Task LoadCollectionsAsync()
         {
             IsLoading = true;