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.Configuration/Enums/NamespaceKind.cs

@@ -0,0 +1,25 @@
+namespace ZB.MOM.WW.OtOpcUa.Configuration.Enums;
+
+/// <summary>OPC UA namespace kind per decision #107. One of each kind per cluster per generation.</summary>
+public enum NamespaceKind
+{
+    /// <summary>
+    ///     Equipment namespace — raw signals from native-protocol drivers (Modbus, AB CIP, AB Legacy,
+    ///     S7, TwinCAT, FOCAS, and OpcUaClient when gatewaying raw equipment). UNS 5-level hierarchy
+    ///     applies.
+    /// </summary>
+    Equipment,
+
+    /// <summary>
+    ///     System Platform namespace — Galaxy / MXAccess processed data (v1 LmxOpcUa folded in).
+    ///     UNS rules do NOT apply; Galaxy hierarchy preserved as v1 expressed it.
+    /// </summary>
+    SystemPlatform,
+
+    /// <summary>
+    ///     Reserved for future replay driver per handoff §"Digital Twin Touchpoints" — not populated
+    ///     in v2.0 but enum value reserved so the schema does not need to change when the replay
+    ///     driver lands.
+    /// </summary>
+    Simulated,
+}