refactor: Remove MailKit and windream DMS dependencies

- Remove IDmsService interface (DMS integration deferred to Phase 5)
- Remove MailKitEmailService implementation
- Remove WindreamDmsService implementation
- Simplify IEmailService to SMTP-only operations
- Preparing for Limilabs Mail.dll migration

BREAKING CHANGE: IEmailService no longer supports IMAP/POP3 operations
Reason: Migrating from MailKit to Limilabs Mail.dll

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

@@ -1,11 +0,0 @@
-namespace DigitalData.EmailProfiler.Application.Common.Interfaces;
-
-/// <summary>
-/// DMS service interface for windream integration.
-/// </summary>
-public interface IDmsService
-{
-    Task<string> ImportDocumentAsync(string filePath, string objectType, Dictionary<string, string> metadata, CancellationToken cancellationToken = default);
-    Task<bool> DocumentExistsAsync(string documentId, CancellationToken cancellationToken = default);
-    Task<bool> UpdateMetadataAsync(string documentId, Dictionary<string, string> metadata, CancellationToken cancellationToken = default);
-}

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

@@ -3,14 +3,16 @@ using DigitalData.EmailProfiler.Application.Common.Dtos;
 namespace DigitalData.EmailProfiler.Application.Common.Interfaces;
 
 /// <summary>
-/// Email service interface for IMAP/SMTP operations.
-/// Implementation uses MailKit.
-/// Throws AuthenticationFailedException when OAuth2/password auth fails.
+/// Email service interface for SMTP operations.
+/// Implementation uses Limilabs Mail.dll for production email sending.
+/// SMTP configuration is injected via IOptions&lt;EmailAccountDto&gt; in appsettings.json.
+/// Throws AuthenticationFailedException when SMTP authentication fails.
 /// </summary>
 public interface IEmailService
 {
-    Task<IEnumerable<object>> ReceiveEmailsAsync(EmailAccountDto account, CancellationToken cancellationToken = default);
-    Task SendEmailAsync(EmailAccountDto account, string to, string subject, string body, bool isHtml = true, CancellationToken cancellationToken = default);
-    Task DeleteEmailAsync(EmailAccountDto account, int imapUid, CancellationToken cancellationToken = default);
-    Task<string> GetOAuth2TokenAsync(string tenantId, string clientId, string clientSecret, CancellationToken cancellationToken = default);
+    /// <summary>
+    /// Sends an email using the configured SMTP account.
+    /// SMTP credentials are configured in appsettings.json (EmailAccount section).
+    /// </summary>
+    Task SendEmailAsync(string to, string subject, string body, bool isHtml = true, CancellationToken cancellationToken = default);
 }