refactor(ui): replace data connections table with TreeView grouped by site

src/ScadaLink.CentralUI/Components/Pages/Admin/DataConnections.razor

@@ -25,50 +25,51 @@
     }
     else
     {
-        <table class="table table-sm table-striped table-hover">
+        <TreeView TItem="DcTreeNode" Items="_treeRoots"
-            <thead class="table-dark">
+                  ChildrenSelector="n => n.Children"
-                <tr>
+                  HasChildrenSelector="n => n.Children.Count > 0"
-                    <th>ID</th>
+                  KeySelector="n => n.Key"
-                    <th>Name</th>
+                  StorageKey="data-connections-tree">
-                    <th>Protocol</th>
+            <NodeContent Context="node">
-                    <th>Site</th>
+                @if (node.Kind == DcNodeKind.Site)
-                    <th>Primary Config</th>
-                    <th>Backup Config</th>
-                    <th style="width: 160px;">Actions</th>
-                </tr>
-            </thead>
-            <tbody>
-                @if (_connections.Count == 0)
                 {
-                    <tr>
+                    <span class="fw-semibold">@node.Label</span>
-                        <td colspan="7" class="text-muted text-center">No data connections configured.</td>
+                    <span class="badge bg-secondary ms-1">@node.Children.Count</span>
-                    </tr>
                 }
-                @foreach (var conn in _connections)
+                else
                 {
-                    <tr>
+                    <span>@node.Label</span>
-                        <td>@conn.Id</td>
+                    <span class="badge bg-info ms-2">@node.Connection!.Protocol</span>
-                        <td>@conn.Name</td>
-                        <td><span class="badge bg-secondary">@conn.Protocol</span></td>
-                        <td>@(_siteLookup.GetValueOrDefault(conn.SiteId)?.Name ?? $"Site {conn.SiteId}")</td>
-                        <td class="text-muted small text-truncate" style="max-width: 300px;">@(conn.PrimaryConfiguration ?? "—")</td>
-                        <td class="text-muted small text-truncate" style="max-width: 300px;">@(conn.BackupConfiguration ?? "—")</td>
-                        <td>
-                            <button class="btn btn-outline-primary btn-sm py-0 px-1 me-1"
-                                    @onclick='() => NavigationManager.NavigateTo($"/admin/data-connections/{conn.Id}/edit")'>Edit</button>
-                            <button class="btn btn-outline-danger btn-sm py-0 px-1"
-                                    @onclick="() => DeleteConnection(conn)">Delete</button>
-                        </td>
-                    </tr>
                 }
-            </tbody>
+            </NodeContent>
-        </table>
+            <ContextMenu Context="node">
+                @if (node.Kind == DcNodeKind.DataConnection)
+                {
+                    <button class="dropdown-item"
+                            @onclick='() => NavigationManager.NavigateTo($"/admin/data-connections/{node.Connection!.Id}/edit")'>
+                        Edit
+                    </button>
+                    <div class="dropdown-divider"></div>
+                    <button class="dropdown-item text-danger"
+                            @onclick="() => DeleteConnection(node.Connection!)">
+                        Delete
+                    </button>
+                }
+            </ContextMenu>
+            <EmptyContent>
+                <span class="text-muted fst-italic">No data connections configured.</span>
+            </EmptyContent>
+        </TreeView>
     }
 </div>
 
 @code {
+    record DcTreeNode(string Key, string Label, DcNodeKind Kind, List<DcTreeNode> Children,
+        DataConnection? Connection = null);
+    enum DcNodeKind { Site, DataConnection }
+
+    private List<DcTreeNode> _treeRoots = new();
     private List<DataConnection> _connections = new();
-    private Dictionary<int, Site> _siteLookup = new();
     private bool _loading = true;
     private string? _errorMessage;
 
@@ -87,8 +88,22 @@
         try
         {
             var sites = await SiteRepository.GetAllSitesAsync();
-            _siteLookup = sites.ToDictionary(s => s.Id);
             _connections = (await SiteRepository.GetAllDataConnectionsAsync()).ToList();
+
+            var connBySite = _connections.GroupBy(c => c.SiteId).ToDictionary(g => g.Key, g => g.ToList());
+            _treeRoots = sites.Select(site => new DcTreeNode(
+                Key: $"site-{site.Id}",
+                Label: site.Name,
+                Kind: DcNodeKind.Site,
+                Children: (connBySite.GetValueOrDefault(site.Id) ?? new())
+                    .Select(c => new DcTreeNode(
+                        Key: $"conn-{c.Id}",
+                        Label: c.Name,
+                        Kind: DcNodeKind.DataConnection,
+                        Children: new(),
+                        Connection: c))
+                    .ToList()
+            )).ToList();
         }
         catch (Exception ex)
         {