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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Addressing/ModbusRegion.cs

@@ -0,0 +1,21 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
+
+/// <summary>
+///     The four Modbus register regions a tag can target. Maps directly to function-code
+///     selection on the wire: <see cref="Coils"/> uses FC01/FC05/FC15, <see cref="DiscreteInputs"/>
+///     uses FC02 (read-only), <see cref="InputRegisters"/> uses FC04 (read-only), and
+///     <see cref="HoldingRegisters"/> uses FC03/FC06/FC16.
+/// </summary>
+/// <remarks>
+///     Lives in the shared addressing assembly so Admin UI and the parser library can speak
+///     about regions without taking a dependency on the wire driver. The driver-side
+///     <c>Driver.Modbus</c> assembly extends the same namespace, so callers see this type as
+///     if it lived in one place.
+/// </remarks>
+public enum ModbusRegion
+{
+    Coils,
+    DiscreteInputs,
+    InputRegisters,
+    HoldingRegisters,
+}