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/Server/ZB.MOM.WW.OtOpcUa.Server.Tests/NodeBootstrapTests.cs

@@ -0,0 +1,63 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Configuration.LocalCache;
+using ZB.MOM.WW.OtOpcUa.Server;
+
+namespace ZB.MOM.WW.OtOpcUa.Server.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class NodeBootstrapTests
+{
+    private sealed class StubCache : ILocalConfigCache
+    {
+        public GenerationSnapshot? Stored { get; set; }
+        public Task<GenerationSnapshot?> GetMostRecentAsync(string _, CancellationToken __) => Task.FromResult(Stored);
+        public Task PutAsync(GenerationSnapshot _, CancellationToken __) => Task.CompletedTask;
+        public Task PruneOldGenerationsAsync(string _, int __, CancellationToken ___) => Task.CompletedTask;
+    }
+
+    [Fact]
+    public async Task Falls_back_to_cache_when_DB_unreachable()
+    {
+        var cache = new StubCache
+        {
+            Stored = new GenerationSnapshot
+            {
+                ClusterId = "c", GenerationId = 42, CachedAt = DateTime.UtcNow, PayloadJson = "{}",
+            },
+        };
+
+        var bootstrap = new NodeBootstrap(
+            new NodeOptions
+            {
+                NodeId = "n",
+                ClusterId = "c",
+                ConfigDbConnectionString = "Server=127.0.0.1,59999;Database=nope;User Id=x;Password=x;TrustServerCertificate=True;Connect Timeout=1;",
+            },
+            cache,
+            NullLogger<NodeBootstrap>.Instance);
+
+        var result = await bootstrap.LoadCurrentGenerationAsync(CancellationToken.None);
+
+        result.Source.ShouldBe(BootstrapSource.LocalCache);
+        result.GenerationId.ShouldBe(42);
+    }
+
+    [Fact]
+    public async Task Throws_BootstrapException_when_DB_unreachable_and_cache_empty()
+    {
+        var bootstrap = new NodeBootstrap(
+            new NodeOptions
+            {
+                NodeId = "n",
+                ClusterId = "c",
+                ConfigDbConnectionString = "Server=127.0.0.1,59999;Database=nope;User Id=x;Password=x;TrustServerCertificate=True;Connect Timeout=1;",
+            },
+            new StubCache(),
+            NullLogger<NodeBootstrap>.Instance);
+
+        await Should.ThrowAsync<BootstrapException>(() =>
+            bootstrap.LoadCurrentGenerationAsync(CancellationToken.None));
+    }
+}