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.Shared/Helpers/SecurityModeMapper.cs

@@ -0,0 +1,42 @@
+using Opc.Ua;
+using ZB.MOM.WW.OtOpcUa.Client.Shared.Models;
+
+namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Helpers;
+
+/// <summary>
+///     Maps between the library's SecurityMode enum and OPC UA SDK MessageSecurityMode.
+/// </summary>
+public static class SecurityModeMapper
+{
+    /// <summary>
+    ///     Converts a <see cref="SecurityMode" /> to an OPC UA <see cref="MessageSecurityMode" />.
+    /// </summary>
+    public static MessageSecurityMode ToMessageSecurityMode(SecurityMode mode)
+    {
+        return mode switch
+        {
+            SecurityMode.None => MessageSecurityMode.None,
+            SecurityMode.Sign => MessageSecurityMode.Sign,
+            SecurityMode.SignAndEncrypt => MessageSecurityMode.SignAndEncrypt,
+            _ => throw new ArgumentOutOfRangeException(nameof(mode), mode, "Unknown SecurityMode value.")
+        };
+    }
+
+    /// <summary>
+    ///     Parses a string to a <see cref="SecurityMode" /> value, case-insensitively.
+    /// </summary>
+    /// <param name="value">The string to parse (e.g., "none", "sign", "encrypt", "signandencrypt").</param>
+    /// <returns>The corresponding SecurityMode.</returns>
+    /// <exception cref="ArgumentException">Thrown for unrecognized values.</exception>
+    public static SecurityMode FromString(string value)
+    {
+        return (value ?? "none").Trim().ToLowerInvariant() switch
+        {
+            "none" => SecurityMode.None,
+            "sign" => SecurityMode.Sign,
+            "encrypt" or "signandencrypt" => SecurityMode.SignAndEncrypt,
+            _ => throw new ArgumentException(
+                $"Unknown security mode '{value}'. Valid values: none, sign, encrypt, signandencrypt")
+        };
+    }
+}