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/Entities/ClusterNode.cs

@@ -0,0 +1,51 @@
+using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
+
+namespace ZB.MOM.WW.OtOpcUa.Configuration.Entities;
+
+/// <summary>Physical OPC UA server node within a <see cref="ServerCluster"/>.</summary>
+public sealed class ClusterNode
+{
+    /// <summary>Stable per-machine logical ID, e.g. "LINE3-OPCUA-A".</summary>
+    public required string NodeId { get; set; }
+
+    public required string ClusterId { get; set; }
+
+    public required RedundancyRole RedundancyRole { get; set; }
+
+    /// <summary>Machine hostname / IP.</summary>
+    public required string Host { get; set; }
+
+    public int OpcUaPort { get; set; } = 4840;
+
+    public int DashboardPort { get; set; } = 8081;
+
+    /// <summary>
+    ///     OPC UA <c>ApplicationUri</c> — MUST be unique per node per OPC UA spec. Clients pin trust here.
+    ///     Fleet-wide unique index enforces no two nodes share a value (decision #86).
+    ///     Stored explicitly, NOT derived from <see cref="Host"/> at runtime — silent rewrite on
+    ///     hostname change would break all client trust.
+    /// </summary>
+    public required string ApplicationUri { get; set; }
+
+    /// <summary>Primary = 200, Secondary = 150 by default.</summary>
+    public byte ServiceLevelBase { get; set; } = 200;
+
+    /// <summary>
+    ///     Per-node override JSON keyed by DriverInstanceId, merged onto cluster-level DriverConfig
+    ///     at apply time. Minimal by intent (decision #81). Nullable when no overrides exist.
+    /// </summary>
+    public string? DriverConfigOverridesJson { get; set; }
+
+    public bool Enabled { get; set; } = true;
+
+    public DateTime? LastSeenAt { get; set; }
+
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+
+    public required string CreatedBy { get; set; }
+
+    // Navigation
+    public ServerCluster? Cluster { get; set; }
+    public ICollection<ClusterNodeCredential> Credentials { get; set; } = [];
+    public ClusterNodeGenerationState? GenerationState { get; set; }
+}