refactor(infrastructure): migrate EmailSyncWorker to DB-backed account source with upsert seed

- EmailSyncWorker now fetches active email accounts from IRepository<EmailAccount>
  on every polling cycle instead of reading from static options list
- Add UpsertSeedEmailAccount: on startup, seed accounts from EmailAccountsOptions
  into the database via IRepository.UpsertAsync (insert or update by Username)
- Remove standalone EmailAccountSyncWorker (merged into EmailSyncWorker)

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Background/EmailAccountSyncWorker.cs

@@ -1,26 +0,0 @@
-using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
-using DigitalData.MessagingService.Application.Common.Options;
-using DigitalData.MessagingService.Domain.Entities;
-using Microsoft.Extensions.Hosting;
-using Microsoft.Extensions.Options;
-
-namespace DigitalData.MessagingService.Infrastructure.Services.Background;
-
-/// <summary>
-/// A hosted background service responsible for initializing the competing email consumer pool.
-/// Leverages a push-based, event-driven RabbitMQ consumer to eliminate polling overhead.
-/// Email account configuration is resolved exclusively from application settings; no database access is performed.
-/// </summary>
-public class EmailAccountSyncWorker(IRepository<EmailAccount> Repository, IOptions<EmailAccountsOptions> Options) : BackgroundService
-{
-    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
-    {
-        foreach (var account in Options.Value.Accounts)
-        {
-            if (account is EmailAccount emailAccount)
-                await Repository.UpsertAsync(a => a.Username == emailAccount.Username, emailAccount, stoppingToken);
-        }
-
-        await Task.Delay(Timeout.Infinite, stoppingToken).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
-    }
-}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Background/EmailSyncWorker.cs

@@ -1,17 +1,22 @@
 using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
 using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
 using DigitalData.MessagingService.Application.Common.Options;
+using DigitalData.MessagingService.Domain.Entities;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Options;
 
 namespace DigitalData.MessagingService.Infrastructure.Services.Background;
 
-public class EmailSyncWorker(IImapEmailService imapService, IOptions<EmailAccountsOptions> Options) : BackgroundService
+public class EmailSyncWorker(IImapEmailService imapService, IOptions<EmailAccountsOptions> Options, IServiceProvider Provider) : BackgroundService
 {
     private DateFilter? _dateFilter = null;
 
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
     {
+        await UpsertSeedEmailAccount(stoppingToken);
+
         if (imapService is not LimilabsImapEmailService limapService)
         {
             await Task.Delay(Timeout.Infinite, stoppingToken).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
@@ -22,7 +27,11 @@ public class EmailSyncWorker(IImapEmailService imapService, IOptions<EmailAccoun
 
         while (!stoppingToken.IsCancellationRequested)
         {
-            foreach (var account in Options.Value.Accounts)
+            using var scope = Provider.CreateAsyncScope();
+
+            var emailAccountRepo = scope.ServiceProvider.GetRequiredService<IRepository<EmailAccount>>();
+
+            foreach (var account in await emailAccountRepo.GetAllAsync(stoppingToken))
                 if (account.ImapServer is not null)
                 {
                     // init or update last date filter
@@ -44,4 +53,15 @@ public class EmailSyncWorker(IImapEmailService imapService, IOptions<EmailAccoun
             await Task.Delay(interval, stoppingToken).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
         }
     }
+
+    public async Task UpsertSeedEmailAccount(CancellationToken stoppingToken)
+    {
+        using var scope = Provider.CreateAsyncScope();
+
+        var emailAccountRepo = scope.ServiceProvider.GetRequiredService<IRepository<EmailAccount>>();
+
+        // init seed email accounts if not exist
+        foreach (var account in Options.Value.Accounts)
+            await emailAccountRepo.UpsertAsync(a => a.Username == account.Username, account, stoppingToken);
+    }
 }