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.Shared/Models/DataChangedEventArgs.cs

@@ -0,0 +1,21 @@
+using Opc.Ua;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Models;
+
+/// <summary>
+///     Event data for a monitored data value change.
+/// </summary>
+public sealed class DataChangedEventArgs : EventArgs
+{
+    public DataChangedEventArgs(string nodeId, DataValue value)
+    {
+        NodeId = nodeId;
+        Value = value;
+    }
+
+    /// <summary>The string representation of the node that changed.</summary>
+    public string NodeId { get; }
+
+    /// <summary>The new data value from the server.</summary>
+    public DataValue Value { get; }
+}