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>

tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeEndpointDiscovery.cs

@@ -0,0 +1,35 @@
+using Opc.Ua;
+using ZB.MOM.WW.OtOpcUa.Client.Shared.Adapters;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Tests.Fakes;
+
+internal sealed class FakeEndpointDiscovery : IEndpointDiscovery
+{
+    public bool ThrowOnSelect { get; set; }
+    public int SelectCallCount { get; private set; }
+    public string? LastEndpointUrl { get; private set; }
+
+    public EndpointDescription SelectEndpoint(ApplicationConfiguration config, string endpointUrl,
+        MessageSecurityMode requestedMode)
+    {
+        SelectCallCount++;
+        LastEndpointUrl = endpointUrl;
+
+        if (ThrowOnSelect)
+            throw new InvalidOperationException($"No endpoint found for {endpointUrl}");
+
+        return new EndpointDescription
+        {
+            EndpointUrl = endpointUrl,
+            SecurityMode = requestedMode,
+            SecurityPolicyUri = requestedMode == MessageSecurityMode.None
+                ? SecurityPolicies.None
+                : SecurityPolicies.Basic256Sha256,
+            Server = new ApplicationDescription
+            {
+                ApplicationName = "FakeServer",
+                ApplicationUri = "urn:localhost:FakeServer"
+            }
+        };
+    }
+}