feat(RemoveAnnotationHandler): add RemoveAnnotationHandler to handle signature removal notifications

- Implements INotificationHandler<RemoveSignatureNotification>
- Deletes Annotation entities matching the Envelope UUID from the repository
- Uses IRepository<Annotation> for data access

EnvelopeGenerator.Application/Common/Notifications/RemoveSignature/Handlers/RemoveAnnotationHandler.cs

@@ -0,0 +1,33 @@
+using DigitalData.Core.Abstraction.Application.Repository;
+using EnvelopeGenerator.Domain.Entities;
+using MediatR;
+
+namespace EnvelopeGenerator.Application.Common.Notifications.RemoveSignature.Handlers;
+
+/// <summary>
+/// 
+/// </summary>
+public class RemoveAnnotationHandler : INotificationHandler<RemoveSignatureNotification>
+{
+    private readonly IRepository<Annotation> _repo;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="repository"></param>
+    public RemoveAnnotationHandler(IRepository<Annotation> repository)
+    {
+        _repo = repository;
+    }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="notification"></param>
+    /// <param name="cancel"></param>
+    /// <returns></returns>
+    public Task Handle(RemoveSignatureNotification notification, CancellationToken cancel)
+    {
+        return _repo.DeleteAsync(a => a.Element!.Document.Envelope!.Uuid == notification.EnvelopeUuid, cancel);
+    }
+}