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/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware/Backend/IAlarmHistorianWriteBackend.cs

@@ -0,0 +1,30 @@
+using System.Threading;
+using System.Threading.Tasks;
+using ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Ipc;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Backend
+{
+    /// <summary>
+    ///     The actual aahClientManaged-bound writer. Extracted so unit tests can
+    ///     substitute a fake without touching the SDK; the production
+    ///     implementation lives in <see cref="SdkAlarmHistorianWriteBackend"/>.
+    /// </summary>
+    /// <remarks>
+    ///     Implementations are responsible for connection management + cluster
+    ///     failover. The wrapping <see cref="AahClientManagedAlarmEventWriter"/>
+    ///     handles batch-level orchestration but delegates the per-event SDK call
+    ///     here so the unit tests can drive every documented MxStatus outcome
+    ///     without an installed AVEVA Historian.
+    /// </remarks>
+    public interface IAlarmHistorianWriteBackend
+    {
+        /// <summary>
+        ///     Persist the supplied events to the historian. Returns one outcome per
+        ///     input slot in the same order — must always return an array of the same
+        ///     length as <paramref name="events"/>.
+        /// </summary>
+        Task<AlarmHistorianWriteOutcome[]> WriteBatchAsync(
+            AlarmHistorianEventDto[] events,
+            CancellationToken cancellationToken);
+    }
+}