feat(email): add tenant draft persistence

Add owner-filtered, job-cascading private draft storage with reversible SQLite and MariaDB migration paths. No API or UI exposes draft content yet.

JobTrackerApi.Tests/EmailDraftPersistenceTests.cs

@@ -0,0 +1,77 @@
+using JobTrackerApi.Data;
+using JobTrackerApi.Models;
+using JobTrackerApi.Services;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Moq;
+using Xunit;
+
+namespace JobTrackerApi.Tests;
+
+public sealed class EmailDraftPersistenceTests
+{
+    [Fact]
+    public async Task Drafts_are_owner_filtered_and_follow_the_owned_job_lifecycle()
+    {
+        await using var connection = new SqliteConnection("Data Source=:memory:");
+        await connection.OpenAsync();
+        var options = new DbContextOptionsBuilder<JobTrackerContext>().UseSqlite(connection).Options;
+
+        int userOneJobId;
+        int userTwoJobId;
+        await using (var seed = Context(options, null))
+        {
+            await seed.Database.EnsureCreatedAsync();
+            var companyOne = new Company { Name = "One", OwnerUserId = "user-1" };
+            var companyTwo = new Company { Name = "Two", OwnerUserId = "user-2" };
+            seed.Companies.AddRange(companyOne, companyTwo);
+            await seed.SaveChangesAsync();
+            var jobOne = new JobApplication { JobTitle = "Role one", CompanyId = companyOne.Id, OwnerUserId = "user-1" };
+            var jobTwo = new JobApplication { JobTitle = "Role two", CompanyId = companyTwo.Id, OwnerUserId = "user-2" };
+            seed.JobApplications.AddRange(jobOne, jobTwo);
+            await seed.SaveChangesAsync();
+            userOneJobId = jobOne.Id;
+            userTwoJobId = jobTwo.Id;
+            seed.EmailDrafts.AddRange(
+                Draft("user-1", jobOne.Id, "one@example.test"),
+                Draft("user-2", jobTwo.Id, "two@example.test"));
+            await seed.SaveChangesAsync();
+        }
+
+        await using (var userOne = Context(options, "user-1"))
+        {
+            var visible = Assert.Single(await userOne.EmailDrafts.AsNoTracking().ToListAsync());
+            Assert.Equal(userOneJobId, visible.JobApplicationId);
+            Assert.Equal("one@example.test", visible.To);
+            var job = await userOne.JobApplications.SingleAsync(item => item.Id == userOneJobId);
+            userOne.JobApplications.Remove(job);
+            await userOne.SaveChangesAsync();
+        }
+
+        await using var verify = Context(options, null);
+        var remaining = Assert.Single(await verify.EmailDrafts.IgnoreQueryFilters().AsNoTracking().ToListAsync());
+        Assert.Equal("user-2", remaining.OwnerUserId);
+        Assert.Equal(userTwoJobId, remaining.JobApplicationId);
+    }
+
+    private static EmailDraft Draft(string ownerUserId, int jobApplicationId, string recipient) => new()
+    {
+        Id = Guid.NewGuid(),
+        OwnerUserId = ownerUserId,
+        JobApplicationId = jobApplicationId,
+        Provider = "gmail",
+        To = recipient,
+        Subject = "Synthetic draft",
+        BodyText = "Synthetic private draft body.",
+        ThreadId = "thread-1",
+        CreatedAtUtc = DateTime.UtcNow,
+        UpdatedAtUtc = DateTime.UtcNow,
+    };
+
+    private static JobTrackerContext Context(DbContextOptions<JobTrackerContext> options, string? userId)
+    {
+        var currentUser = new Mock<ICurrentUserService>();
+        currentUser.SetupGet(service => service.UserId).Returns(userId);
+        return new JobTrackerContext(options, currentUser.Object);
+    }
+}