feat(infrastructure): Add Limilabs email service and RabbitMQ email queue

- Add LimilabsEmailService for SMTP operations (IEmailService implementation)
- Add RabbitMqEmailQueue for production email queue (RabbitMQ-based)
- Update InMemoryEmailQueue for improved error handling
- Update IEmailQueue interface for RabbitMQ compatibility
- Update DependencyInjection.cs:
  * Switch IEmailService to LimilabsEmailService (Singleton)
  * Switch IEmailQueue to RabbitMqEmailQueue (Singleton)
  * Change IEncryptionService to Singleton (thread-safe)
  * Remove IDmsService registration
- Add required NuGet package references to .csproj

TODO: Add Limilabs.Mail NuGet package (commercial license required)

src/DigitalData.EmailProfiler.Infrastructure/DependencyInjection.cs

@@ -1,10 +1,7 @@
 using DigitalData.EmailProfiler.Application.Common.Interfaces;
 using DigitalData.EmailProfiler.Infrastructure.Messaging;
-using DigitalData.EmailProfiler.Infrastructure.Persistence;
 using DigitalData.EmailProfiler.Infrastructure.Queue;
-using DigitalData.EmailProfiler.Infrastructure.Repositories;
 using DigitalData.EmailProfiler.Infrastructure.Services;
-using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -22,30 +19,18 @@ public static class DependencyInjection
         this IServiceCollection services,
         IConfiguration configuration)
     {
-        // --- Database Context ---
-        services.AddDbContext<EmailProfilerDbContext>(options =>
-            options.UseSqlServer(
-                configuration.GetConnectionString("DefaultConnection"),
-                sqlOptions => sqlOptions.EnableRetryOnFailure()));
-
-        // --- Generic Repository ---
-        services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
-
         // --- External Services ---
-        // Email Service (using MailKit/MimeKit with OAuth2)
-        services.AddScoped<IEmailService, MailKitEmailService>();
+        // Email Service (using Limilabs Mail.dll - Singleton for use in EmailSenderWorker)
+        services.AddSingleton<IEmailService, LimilabsEmailService>();
         
         // PDF Processing Service (using DevExpress.Pdf)
         services.AddScoped<IPdfProcessingService, DevExpressPdfProcessingService>();
         
-        // DMS Service (using windream COM Interop)
-        services.AddScoped<IDmsService, WindreamDmsService>();
-        
-        // Encryption Service (using Data Protection API)
-        services.AddScoped<IEncryptionService, DataProtectionEncryptionService>();
+        // Encryption Service (using Data Protection API - Singleton, thread-safe)
+        services.AddSingleton<IEncryptionService, DataProtectionEncryptionService>();
 
-        // --- Email Queue ---
-        services.AddSingleton<IEmailQueue, InMemoryEmailQueue>();
+        // --- Email Queue (RabbitMQ) ---
+        services.AddSingleton<IEmailQueue, RabbitMqEmailQueue>();
 
         // --- RabbitMQ Configuration ---
         services.Configure<RabbitMqConfiguration>(