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/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Services/AvaloniaUiDispatcher.cs

@@ -0,0 +1,14 @@
+using Avalonia.Threading;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.UI.Services;
+
+/// <summary>
+///     Dispatches actions to the Avalonia UI thread.
+/// </summary>
+public sealed class AvaloniaUiDispatcher : IUiDispatcher
+{
+    public void Post(Action action)
+    {
+        Dispatcher.UIThread.Post(action);
+    }
+}

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Services/ISettingsService.cs

@@ -0,0 +1,10 @@
+namespace ZB.MOM.WW.OtOpcUa.Client.UI.Services;
+
+/// <summary>
+/// Loads and saves user settings.
+/// </summary>
+public interface ISettingsService
+{
+    UserSettings Load();
+    void Save(UserSettings settings);
+}

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Services/IUiDispatcher.cs

@@ -0,0 +1,12 @@
+namespace ZB.MOM.WW.OtOpcUa.Client.UI.Services;
+
+/// <summary>
+///     Abstraction for dispatching actions to the UI thread.
+/// </summary>
+public interface IUiDispatcher
+{
+    /// <summary>
+    ///     Posts an action to be executed on the UI thread.
+    /// </summary>
+    void Post(Action action);
+}

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Services/JsonSettingsService.cs

@@ -0,0 +1,51 @@
+using System.Text.Json;
+using ZB.MOM.WW.OtOpcUa.Client.Shared;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.UI.Services;
+
+/// <summary>
+/// Persists user settings to a JSON file under LocalApplicationData.
+/// </summary>
+public sealed class JsonSettingsService : ISettingsService
+{
+    // ClientStoragePaths.GetRoot runs the one-shot legacy-folder migration so pre-#208
+    // developer boxes pick up their existing settings.json on first launch post-rename.
+    private static readonly string SettingsDir = ClientStoragePaths.GetRoot();
+
+    private static readonly string SettingsPath = Path.Combine(SettingsDir, "settings.json");
+
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        WriteIndented = true
+    };
+
+    public UserSettings Load()
+    {
+        try
+        {
+            if (!File.Exists(SettingsPath))
+                return new UserSettings();
+
+            var json = File.ReadAllText(SettingsPath);
+            return JsonSerializer.Deserialize<UserSettings>(json, JsonOptions) ?? new UserSettings();
+        }
+        catch
+        {
+            return new UserSettings();
+        }
+    }
+
+    public void Save(UserSettings settings)
+    {
+        try
+        {
+            Directory.CreateDirectory(SettingsDir);
+            var json = JsonSerializer.Serialize(settings, JsonOptions);
+            File.WriteAllText(SettingsPath, json);
+        }
+        catch
+        {
+            // Best-effort save; don't crash the app
+        }
+    }
+}

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Services/SynchronousUiDispatcher.cs

@@ -0,0 +1,13 @@
+namespace ZB.MOM.WW.OtOpcUa.Client.UI.Services;
+
+/// <summary>
+///     Dispatcher that executes actions synchronously on the calling thread.
+///     Used for unit testing where no UI thread is available.
+/// </summary>
+public sealed class SynchronousUiDispatcher : IUiDispatcher
+{
+    public void Post(Action action)
+    {
+        action();
+    }
+}

src/Client/ZB.MOM.WW.OtOpcUa.Client.UI/Services/UserSettings.cs

@@ -0,0 +1,59 @@
+using ZB.MOM.WW.OtOpcUa.Client.Shared.Models;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.UI.Services;
+
+/// <summary>
+/// Persisted user connection settings.
+/// </summary>
+public sealed class UserSettings
+{
+    /// <summary>
+    /// Gets or sets the last OPC UA endpoint URL entered by the user.
+    /// </summary>
+    public string EndpointUrl { get; set; } = "opc.tcp://localhost:4840";
+
+    /// <summary>
+    /// Gets or sets the persisted username for authenticated sessions.
+    /// </summary>
+    public string? Username { get; set; }
+
+    /// <summary>
+    /// Gets or sets the persisted password for authenticated sessions.
+    /// </summary>
+    public string? Password { get; set; }
+
+    /// <summary>
+    /// Gets or sets the transport security mode selected by the user.
+    /// </summary>
+    public SecurityMode SecurityMode { get; set; } = SecurityMode.None;
+
+    /// <summary>
+    /// Gets or sets the raw failover endpoint list entered in the UI.
+    /// </summary>
+    public string? FailoverUrls { get; set; }
+
+    /// <summary>
+    /// Gets or sets the persisted session timeout, in seconds, for new client connections.
+    /// </summary>
+    public int SessionTimeoutSeconds { get; set; } = 60;
+
+    /// <summary>
+    /// Gets or sets a value indicating whether untrusted server certificates should be auto-accepted.
+    /// </summary>
+    public bool AutoAcceptCertificates { get; set; } = true;
+
+    /// <summary>
+    /// Gets or sets the certificate store path used for client certificates and trust lists.
+    /// </summary>
+    public string? CertificateStorePath { get; set; }
+
+    /// <summary>
+    /// Gets or sets the node IDs that should be re-subscribed when the UI reconnects.
+    /// </summary>
+    public List<string> SubscribedNodes { get; set; } = [];
+
+    /// <summary>
+    /// Gets or sets the alarm source node that should be restored when the UI reconnects.
+    /// </summary>
+    public string? AlarmSourceNodeId { get; set; }
+}