Refactor: Replace EmailAttachmentContext with DTO

Replaced `EmailAttachmentContext` with `EmailAttachmentDto` across the codebase to align with the updated DTO naming convention.

- Renamed `EmailAttachmentContext` to `EmailAttachmentDto`.
- Updated property types, method signatures, and return types to use `EmailAttachmentDto`.
- Modified XML documentation references to reflect the new class name.
- Updated `ReceivedEmailContext` to `ReceivedEmailDto` and adjusted related methods and properties.
- Refactored `FetchEmailsAsync` methods and handlers to use `ReceivedEmailDto`.
- Adjusted `BuildAttachmentsAsync` and attachment handling logic in `EmailController` and `LimilabsImapEmailService`.

This refactor ensures consistency and improves code clarity while maintaining functionality.

src/core/DigitalData.MessagingService.Application/Common/Interfaces/IImapEmailService.cs

@@ -17,7 +17,7 @@ public interface IImapEmailService
     /// Set to <see langword="false"/> for a non-destructive read (uses <c>BODY.PEEK</c> internally).
     /// </param>
     /// <param name="cancellationToken">Cancellation token.</param>
-    Task<IEnumerable<ReceivedEmailContext>> FetchEmailsAsync(
+    Task<IEnumerable<ReceivedEmailDto>> FetchEmailsAsync(
         EmailAccountDto account,
         MailSearchFilter filter,
         CancellationToken cancellationToken = default);

src/core/DigitalData.MessagingService.Application/EmailReceiving/Queries/FetchEmailsQuery.cs

@@ -10,7 +10,7 @@ namespace DigitalData.MessagingService.Application.EmailReceiving.Queries;
 /// <summary>
 /// Query to fetch emails from an IMAP mailbox.
 /// </summary>
-public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailContext>>
+public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailDto>>
 {
     /// <summary>
     /// Identifies the email account to use.
@@ -25,9 +25,9 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailContext>>
 
 public class FetchEmailsQueryHandler(
     ISender Sender,
-    IImapEmailService ImapService) : IRequestHandler<FetchEmailsQuery, IEnumerable<ReceivedEmailContext>>
+    IImapEmailService ImapService) : IRequestHandler<FetchEmailsQuery, IEnumerable<ReceivedEmailDto>>
 {
-    public async Task<IEnumerable<ReceivedEmailContext>> Handle(FetchEmailsQuery request, CancellationToken cancellationToken)
+    public async Task<IEnumerable<ReceivedEmailDto>> Handle(FetchEmailsQuery request, CancellationToken cancellationToken)
     {
         var account = await Sender.Send(request.Account, cancellationToken)
             ?? throw new NotFoundException(

src/core/DigitalData.MessagingService.Application/EmailSending/Commands/PublishEmailCommand.cs

@@ -35,13 +35,13 @@ public record PublishEmailCommand : IRequest<Guid>
     public bool IsHtml { get; init; } = true;
 
     [JsonIgnore]
-    internal IEnumerable<EmailAttachmentContext> Attachments { get; private init; } = [];
+    internal IEnumerable<EmailAttachmentDto> Attachments { get; private init; } = [];
 
     /// <summary>
     /// Returns a new command instance with the supplied attachments.
     /// Called by the controller after resolving uploaded files.
     /// </summary>
-    public PublishEmailCommand WithAttachments(IEnumerable<EmailAttachmentContext> attachments)
+    public PublishEmailCommand WithAttachments(IEnumerable<EmailAttachmentDto> attachments)
         => this with { Attachments = attachments };
 }