refactor(application): Remove IUnitOfWork, add generic IRepository<T> with AutoMapper

- Remove IUnitOfWork pattern (not needed with auto-save repositories)
- Add generic IRepository<T> with CreateAsync<TDto>, UpdateSingleAsync<TDto>, DeleteSingleAsync
- Add UpdateAsync/DeleteAsync for bulk operations
- Add ICommandPublisher interface for RabbitMQ integration
- Add service interfaces: IEmailService, IPdfProcessingService, IDmsService, IEncryptionService, IEmailQueue
- Configure Application DI with MediatR, AutoMapper, FluentValidation

src/DigitalData.EmailProfiler.Application/Common/Interfaces/ICommandPublisher.cs

@@ -0,0 +1,19 @@
+using MediatR;
+
+namespace DigitalData.EmailProfiler.Application.Common.Interfaces;
+
+/// <summary>
+/// Interface for publishing commands to a message broker (e.g., RabbitMQ)
+/// </summary>
+public interface ICommandPublisher
+{
+    /// <summary>
+    /// Publishes a command to the message broker for asynchronous processing
+    /// </summary>
+    /// <typeparam name="TCommand">The command type (must implement IRequest)</typeparam>
+    /// <param name="command">The command to publish</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Task representing the publish operation</returns>
+    Task PublishAsync<TCommand>(TCommand command, CancellationToken cancellationToken = default) 
+        where TCommand : IRequest;
+}