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.Core.Abstractions/DriverHealth.cs

@@ -0,0 +1,38 @@
+namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+/// <summary>
+///     Health snapshot a driver returns to the Core. Drives the status dashboard,
+///     ServiceLevel computation, and Bad-quality fan-out decisions.
+/// </summary>
+/// <param name="State">Current driver-instance state.</param>
+/// <param name="LastSuccessfulRead">Timestamp of the most recent successful equipment read; null if never.</param>
+/// <param name="LastError">Most recent error message; null when state is Healthy.</param>
+public sealed record DriverHealth(
+    DriverState State,
+    DateTime? LastSuccessfulRead,
+    string? LastError);
+
+/// <summary>Driver-instance lifecycle state.</summary>
+public enum DriverState
+{
+    /// <summary>Driver has not been initialized yet.</summary>
+    Unknown,
+
+    /// <summary>Driver is in the middle of <see cref="IDriver.InitializeAsync"/> or <see cref="IDriver.ReinitializeAsync"/>.</summary>
+    Initializing,
+
+    /// <summary>Driver is connected and serving data.</summary>
+    Healthy,
+
+    /// <summary>Driver is connected but reporting degraded data (e.g. some equipment unreachable, some tags Bad).</summary>
+    Degraded,
+
+    /// <summary>Driver lost connection to its data source; reconnecting in the background.</summary>
+    Reconnecting,
+
+    /// <summary>
+    ///     Driver hit an unrecoverable error and stopped trying.
+    ///     Operator must reinitialize via Admin UI; nodes report Bad quality.
+    /// </summary>
+    Faulted,
+}