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/Server/ZB.MOM.WW.OtOpcUa.Admin/Hubs/AlertHub.cs

@@ -0,0 +1,31 @@
+using Microsoft.AspNetCore.SignalR;
+
+namespace ZB.MOM.WW.OtOpcUa.Admin.Hubs;
+
+/// <summary>
+///     Pushes sticky alerts (crash-loop circuit trips, failed applies, reservation-release
+///     anomalies) to subscribed admin clients. Alerts don't auto-clear — the operator acks them
+///     from the UI via <see cref="AcknowledgeAsync"/>.
+/// </summary>
+public sealed class AlertHub : Hub
+{
+    public const string AllAlertsGroup = "__alerts__";
+
+    public override async Task OnConnectedAsync()
+    {
+        await Groups.AddToGroupAsync(Context.ConnectionId, AllAlertsGroup);
+        await base.OnConnectedAsync();
+    }
+
+    /// <summary>Client-initiated ack. The server side of ack persistence is deferred — v2.1.</summary>
+    public Task AcknowledgeAsync(string alertId) => Task.CompletedTask;
+}
+
+public sealed record AlertMessage(
+    string AlertId,
+    string Severity,
+    string Title,
+    string Detail,
+    DateTime RaisedAtUtc,
+    string? ClusterId,
+    string? NodeId);