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/SecurityClassification.cs

@@ -0,0 +1,23 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     Security classification for write authorization on a tag, mirroring
+///     the v1 Galaxy SecurityClassification model documented in <c>docs/DataTypeMapping.md</c>.
+///     Generalized so non-Galaxy drivers can declare per-tag write protection levels.
+/// </summary>
+/// <remarks>
+///     Maps to <c>NodePermissions</c> write tiers in <c>docs/v2/acl-design.md</c>:
+///     FreeAccess + Operate require <c>WriteOperate</c>; Tune requires <c>WriteTune</c>;
+///     Configure requires <c>WriteConfigure</c>; SecuredWrite + VerifiedWrite + ViewOnly
+///     are read-only from OPC UA (v1 behavior preserved).
+/// </remarks>
+public enum SecurityClassification
+{
+    FreeAccess = 0,
+    Operate = 1,
+    SecuredWrite = 2,
+    VerifiedWrite = 3,
+    Tune = 4,
+    Configure = 5,
+    ViewOnly = 6,
+}