refactor(notify): merge Notifier WebService into Notify WebService

- Delete dead Notify Worker (NoOp handler)
- Move 51 source files (endpoints, contracts, services, compat stores)
- Transform namespaces from Notifier.WebService to Notify.WebService
- Update DI registrations, WebSocket support, v2 endpoint mapping
- Comment out notifier-web in compose, update gateway routes
- Update architecture docs, port registry, rollout matrix
- Notifier Worker stays as separate delivery engine container

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Notify/StellaOps.Notify.WebService/Setup/NullNotifyEventQueue.cs

@@ -0,0 +1,22 @@
+
+using StellaOps.Notify.Queue;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace StellaOps.Notify.WebService.Setup;
+
+/// <summary>
+/// No-op event queue used when a real queue backend is not configured (dev/test/offline).
+/// </summary>
+public sealed class NullNotifyEventQueue : INotifyEventQueue
+{
+    public ValueTask<NotifyQueueEnqueueResult> PublishAsync(NotifyQueueEventMessage message, CancellationToken cancellationToken = default) =>
+        ValueTask.FromResult(new NotifyQueueEnqueueResult("null", false));
+
+    public ValueTask<IReadOnlyList<INotifyQueueLease<NotifyQueueEventMessage>>> LeaseAsync(NotifyQueueLeaseRequest request, CancellationToken cancellationToken = default) =>
+        ValueTask.FromResult<IReadOnlyList<INotifyQueueLease<NotifyQueueEventMessage>>>(Array.Empty<INotifyQueueLease<NotifyQueueEventMessage>>());
+
+    public ValueTask<IReadOnlyList<INotifyQueueLease<NotifyQueueEventMessage>>> ClaimExpiredAsync(NotifyQueueClaimOptions options, CancellationToken cancellationToken = default) =>
+        ValueTask.FromResult<IReadOnlyList<INotifyQueueLease<NotifyQueueEventMessage>>>(Array.Empty<INotifyQueueLease<NotifyQueueEventMessage>>());
+}