feat(email): export send attempt metadata

Add content-free provider delivery history to encrypted and daily owner exports, exclude payload hashes, and lock in tenant-safe hard-delete cascades.

JobTrackerApi/Models/EmailSendAttempt.cs

@@ -25,3 +25,15 @@ public sealed class EmailSendAttempt
     public DateTime? StartedAtUtc { get; set; }
     public DateTime? CompletedAtUtc { get; set; }
 }
+
+public sealed record EmailSendAttemptExport(
+    Guid Id,
+    int JobApplicationId,
+    string Provider,
+    string ClientRequestId,
+    string Status,
+    string? ProviderMessageId,
+    string? FailureCategory,
+    DateTime CreatedAtUtc,
+    DateTime? StartedAtUtc,
+    DateTime? CompletedAtUtc);