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/Apply/ApplyCallbacks.cs

@@ -0,0 +1,19 @@
+using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
+
+namespace ZB.MOM.WW.OtOpcUa.Configuration.Apply;
+
+/// <summary>
+///     Host-supplied callbacks invoked as the applier walks the diff. Callbacks are idempotent on
+///     retry (the applier may re-invoke with the same inputs if a later stage fails — nodes
+///     register-applied to the central DB only after success). Order: namespace → driver → device →
+///     equipment → poll group → tag, with Removed before Added/Modified.
+/// </summary>
+public sealed class ApplyCallbacks
+{
+    public Func<EntityChange<Namespace>, CancellationToken, Task>? OnNamespace { get; init; }
+    public Func<EntityChange<DriverInstance>, CancellationToken, Task>? OnDriver { get; init; }
+    public Func<EntityChange<Device>, CancellationToken, Task>? OnDevice { get; init; }
+    public Func<EntityChange<Equipment>, CancellationToken, Task>? OnEquipment { get; init; }
+    public Func<EntityChange<PollGroup>, CancellationToken, Task>? OnPollGroup { get; init; }
+    public Func<EntityChange<Tag>, CancellationToken, Task>? OnTag { get; init; }
+}