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/integration/run-focas.ps1

@@ -52,7 +52,7 @@ Set-StrictMode -Version 3.0
 $ErrorActionPreference = "Stop"
 
 $repoRoot   = (Resolve-Path (Join-Path $PSScriptRoot "..\..")).Path
-$integTests = Join-Path $repoRoot "tests\ZB.MOM.WW.OtOpcUa.Driver.FOCAS.IntegrationTests"
+$integTests = Join-Path $repoRoot "tests\Drivers\ZB.MOM.WW.OtOpcUa.Driver.FOCAS.IntegrationTests"
 $dockerYml  = Join-Path $integTests "Docker\docker-compose.yml"
 
 function Write-Step { param([string]$Msg) Write-Host ""; Write-Host "=== $Msg ===" -ForegroundColor Cyan }