feat(email): add delivery adapters

Gmail and Graph request explicit send consent and classify provider rejection separately from uncertain transport failure. IMAP remains read-only; no send API is exposed.

JobTrackerApi/Services/EmailProviders/GmailProvider.cs

@@ -21,7 +21,7 @@ namespace JobTrackerApi.Services.EmailProviders
         public async Task<EmailConnectionInfo?> GetConnectionAsync(string ownerUserId, CancellationToken cancellationToken)
         {
             var connection = await _gmail.GetConnectionAsync(ownerUserId, cancellationToken);
-            return connection is null ? null : new EmailConnectionInfo("gmail", connection.GmailAddress ?? "");
+            return connection is null ? null : new EmailConnectionInfo("gmail", connection.GmailAddress ?? "", GmailOAuthService.HasSendScope(connection.Scope));
         }
 
         public async Task<IReadOnlyList<EmailMessageSummary>> SearchAsync(string ownerUserId, string? query, int maxResults, CancellationToken cancellationToken)
@@ -57,6 +57,12 @@ namespace JobTrackerApi.Services.EmailProviders
                 attachments);
         }
 
+        public async Task<EmailDeliveryResult> SendAsync(string ownerUserId, EmailDeliveryRequest request, CancellationToken cancellationToken)
+        {
+            var result = await _gmail.SendAsync(ownerUserId, new GmailSendRequest(request.To, request.Subject, request.BodyText, request.ThreadId), cancellationToken);
+            return new EmailDeliveryResult(result.MessageId, result.ThreadId);
+        }
+
         private static EmailMessageSummary ToSummary(GmailMessageSummary m)
             => new(m.Id, m.ThreadId, m.Subject, m.From, m.To, m.Date, m.Snippet);
     }