feat(email): add explicit send API

Require tenant-owned jobs, explicit confirmation, canonical request IDs, and rate limiting before provider delivery. Persist sent correspondence with a content-free idempotency ledger, and never retry uncertain outcomes automatically.

JobTrackerApi.Tests/EmailControllerTests.cs

@@ -3,6 +3,9 @@ using JobTrackerApi.Controllers;
 using JobTrackerApi.Services.EmailProviders;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Logging.Abstractions;
+using JobTrackerApi.Services;
+using JobTrackerApi.Tests.TestSupport;
 using Xunit;
 
 namespace JobTrackerApi.Tests;
@@ -67,7 +70,8 @@ public sealed class EmailControllerTests
 
     private static EmailController CreateController(params IEmailProvider[] providers)
     {
-        var controller = new EmailController(new EmailProviderRegistry(providers));
+        var db = TestHostFactory.CreateInMemoryDb();
+        var controller = new EmailController(new EmailProviderRegistry(providers), db, new EmailSendAttemptStore(db, TimeProvider.System), NullLogger<EmailController>.Instance);
         controller.ControllerContext = new ControllerContext
         {
             HttpContext = new DefaultHttpContext