chore: organize solution into module folders (Core/Server/Drivers/Client/Tooling)

Group all 69 projects into category subfolders under src/ and tests/ so the
Rider Solution Explorer mirrors the module structure. Folders: Core, Server,
Drivers (with a nested Driver CLIs subfolder), Client, Tooling.

- Move every project folder on disk with git mv (history preserved as renames).
- Recompute relative paths in 57 .csproj files: cross-category ProjectReferences,
  the lib/ HintPath+None refs in Driver.Historian.Wonderware, and the external
  mxaccessgw refs in Driver.Galaxy and its test project.
- Rebuild ZB.MOM.WW.OtOpcUa.slnx with nested solution folders.
- Re-prefix project paths in functional scripts (e2e, compliance, smoke SQL,
  integration, install).

Build green (0 errors); unit tests pass. Docs left for a separate pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Views/BrowseTreeView.axaml

@@ -0,0 +1,31 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:vm="using:ZB.MOM.WW.OtOpcUa.Client.UI.ViewModels"
+             x:Class="ZB.MOM.WW.OtOpcUa.Client.UI.Views.BrowseTreeView"
+             x:DataType="vm:BrowseTreeViewModel">
+    <TreeView ItemsSource="{Binding RootNodes}"
+              Name="BrowseTree"
+              SelectionMode="Multiple">
+        <TreeView.Styles>
+            <Style Selector="TreeViewItem" x:DataType="vm:TreeNodeViewModel">
+                <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
+            </Style>
+        </TreeView.Styles>
+        <TreeView.ItemTemplate>
+            <TreeDataTemplate ItemsSource="{Binding Children}">
+                <StackPanel Orientation="Horizontal" Spacing="6">
+                    <TextBlock Text="{Binding DisplayName}" VerticalAlignment="Center" />
+                    <TextBlock Text="{Binding NodeClass}"
+                               FontSize="10"
+                               Foreground="Gray"
+                               VerticalAlignment="Center" />
+                    <ProgressBar IsIndeterminate="True"
+                                 IsVisible="{Binding IsLoading}"
+                                 Width="50"
+                                 Height="8"
+                                 VerticalAlignment="Center" />
+                </StackPanel>
+            </TreeDataTemplate>
+        </TreeView.ItemTemplate>
+    </TreeView>
+</UserControl>