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/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/DataValueSnapshot.cs

@@ -0,0 +1,21 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     Driver-agnostic value snapshot returned by <see cref="IReadable"/> and pushed
+///     by <see cref="ISubscribable.OnDataChange"/>. Mirrors the OPC UA <c>DataValue</c>
+///     shape so the node-manager can pass through quality, source timestamp, and
+///     server timestamp without translation.
+/// </summary>
+/// <remarks>
+///     Per <c>docs/v2/plan.md</c> decision #13 — every driver maps to the same
+///     OPC UA StatusCode space; this DTO is the universal carrier.
+/// </remarks>
+/// <param name="Value">The raw value; null when <see cref="StatusCode"/> indicates Bad.</param>
+/// <param name="StatusCode">OPC UA status code (numeric value matches the OPC UA spec).</param>
+/// <param name="SourceTimestampUtc">Driver-side timestamp when the value was sampled at the source. Null if unavailable.</param>
+/// <param name="ServerTimestampUtc">Driver-side timestamp when the driver received / processed the value.</param>
+public sealed record DataValueSnapshot(
+    object? Value,
+    uint StatusCode,
+    DateTime? SourceTimestampUtc,
+    DateTime ServerTimestampUtc);