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>

scripts/e2e/test-modbus.ps1

@@ -1,4 +1,4 @@
-#Requires -Version 7.0
+#Requires -Version 7.0
 <#
 .SYNOPSIS
   End-to-end CLI test for the Modbus-TCP driver bridged through the OtOpcUa server.
@@ -48,10 +48,10 @@ $hostPart, $portPart = $ModbusHost.Split(":")
 $port = [int]$portPart
 
 $modbusCli = Get-CliInvocation `
-    -ProjectFolder "src/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli" `
+    -ProjectFolder "src/Drivers/Cli/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli" `
     -ExeName "otopcua-modbus-cli"
 $opcUaCli = Get-CliInvocation `
-    -ProjectFolder "src/ZB.MOM.WW.OtOpcUa.Client.CLI" `
+    -ProjectFolder "src/Client/ZB.MOM.WW.OtOpcUa.Client.CLI" `
     -ExeName "otopcua-cli"
 
 $commonModbus = @("-h", $hostPart, "-p", $port)