feat: deterministic email-driven status suggestions

New EmailStatusClassifier scans a message subject/body for outcome
signals (interview invite, offer, rejection) and suggests a canonical
pipeline status. Priority-ordered so a rejection that mentions the prior
interview still classifies as Rejected. Deterministic - no AI - so it is
instant, reproducible, and safe.

- GET /api/jobapplications/{id}/status-suggestion reads the job's latest
  inbound correspondence (incl. Gmail imports) and suggests a forward
  status move, suppressed when already in/past that stage
- always human-confirmed via the existing PATCH .../status
- 7 classifier unit tests + 2 endpoint integration tests; backend green (133)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

JobTrackerApi.Tests/EmailStatusClassifierTests.cs

@@ -0,0 +1,61 @@
+using JobTrackerApi.Services;
+using Xunit;
+
+namespace JobTrackerApi.Tests;
+
+public sealed class EmailStatusClassifierTests
+{
+    [Fact]
+    public void Detects_rejection()
+    {
+        var s = EmailStatusClassifier.Classify("Your application", "Thank you for your time. Unfortunately, we have decided not to proceed with your application.");
+        Assert.NotNull(s);
+        Assert.Equal("Rejected", s!.SuggestedStatus);
+    }
+
+    [Fact]
+    public void Detects_offer()
+    {
+        var s = EmailStatusClassifier.Classify("Great news", "We are pleased to offer you the position of Backend Engineer.");
+        Assert.NotNull(s);
+        Assert.Equal("Offer", s!.SuggestedStatus);
+    }
+
+    [Fact]
+    public void Detects_interview_invite()
+    {
+        var s = EmailStatusClassifier.Classify("Next steps", "We would like to invite you to interview next week. What is your availability for a call?");
+        Assert.NotNull(s);
+        Assert.Equal("Interview", s!.SuggestedStatus);
+    }
+
+    [Fact]
+    public void Rejection_wins_over_interview_mention()
+    {
+        // A rejection email that references the interview the candidate had must classify as Rejected.
+        var s = EmailStatusClassifier.Classify(
+            "Update on your application",
+            "Thank you for taking the time to interview with us. Unfortunately, we will not be moving forward.");
+        Assert.NotNull(s);
+        Assert.Equal("Rejected", s!.SuggestedStatus);
+    }
+
+    [Fact]
+    public void Weak_interview_cue_is_low_confidence()
+    {
+        var s = EmailStatusClassifier.Classify("Coding challenge", "Please complete this take-home assessment.");
+        Assert.NotNull(s);
+        Assert.Equal("Interview", s!.SuggestedStatus);
+        Assert.Equal("low", s.Confidence);
+    }
+
+    [Fact]
+    public void Returns_null_for_neutral_email()
+    {
+        Assert.Null(EmailStatusClassifier.Classify("Re: question", "Thanks for the info, that answers my question about the parking."));
+    }
+
+    [Fact]
+    public void Handles_empty_input()
+        => Assert.Null(EmailStatusClassifier.Classify(null, null));
+}

JobTrackerApi.Tests/JobApplicationsEndpointBehaviorTests.cs

@@ -56,6 +56,68 @@ public sealed class JobApplicationsEndpointBehaviorTests
         Assert.Contains("Profile page", badRequest.Value?.ToString());
     }
 
+    [Fact]
+    public async Task Status_suggestion_from_latest_inbound_rejection()
+    {
+        await using var db = CreateDb();
+        var company = new Company { Name = "Acme", OwnerUserId = "user-1" };
+        db.Companies.Add(company);
+        await db.SaveChangesAsync();
+
+        var job = new JobApplication { JobTitle = "Dev", CompanyId = company.Id, OwnerUserId = "user-1", Status = "Applied" };
+        db.JobApplications.Add(job);
+        await db.SaveChangesAsync();
+
+        db.Correspondences.Add(new Correspondence
+        {
+            JobApplicationId = job.Id,
+            From = "Company",
+            Direction = "inbound",
+            Subject = "Update",
+            Content = "Unfortunately, we have decided not to proceed.",
+            Date = DateTime.Now,
+        });
+        await db.SaveChangesAsync();
+
+        var controller = CreateController(db, "user-1");
+        var result = await controller.GetStatusSuggestion(job.Id, CancellationToken.None);
+
+        var ok = Assert.IsType<OkObjectResult>(result.Result);
+        var dto = Assert.IsType<JobApplicationsController.StatusSuggestionDto>(ok.Value);
+        Assert.True(dto.HasSuggestion);
+        Assert.Equal("Rejected", dto.SuggestedStatus);
+    }
+
+    [Fact]
+    public async Task Status_suggestion_suppressed_when_already_in_stage()
+    {
+        await using var db = CreateDb();
+        var company = new Company { Name = "Acme", OwnerUserId = "user-1" };
+        db.Companies.Add(company);
+        await db.SaveChangesAsync();
+
+        var job = new JobApplication { JobTitle = "Dev", CompanyId = company.Id, OwnerUserId = "user-1", Status = "Rejected" };
+        db.JobApplications.Add(job);
+        await db.SaveChangesAsync();
+
+        db.Correspondences.Add(new Correspondence
+        {
+            JobApplicationId = job.Id,
+            From = "Company",
+            Direction = "inbound",
+            Content = "Unfortunately, we will not be moving forward.",
+            Date = DateTime.Now,
+        });
+        await db.SaveChangesAsync();
+
+        var controller = CreateController(db, "user-1");
+        var result = await controller.GetStatusSuggestion(job.Id, CancellationToken.None);
+
+        var ok = Assert.IsType<OkObjectResult>(result.Result);
+        var dto = Assert.IsType<JobApplicationsController.StatusSuggestionDto>(ok.Value);
+        Assert.False(dto.HasSuggestion);
+    }
+
     [Fact]
     public async Task Match_score_scores_job_against_profile_cv()
     {