feat(profile): /profile/update_official_mark_display

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.UnitTests/Controllers/ProfileControllerUpdateOfficialMarkDisplayTests.cs

@@ -0,0 +1,33 @@
+// SVSim.UnitTests/Controllers/ProfileControllerUpdateOfficialMarkDisplayTests.cs
+using System.Net;
+using System.Text;
+using NUnit.Framework;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Controllers;
+
+public class ProfileControllerUpdateOfficialMarkDisplayTests
+{
+    [TestCase(0, false)]
+    [TestCase(1, true)]
+    public async Task UpdateOfficialMarkDisplay_persists_flag(int wireValue, bool expected)
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(tutorialState: 0);
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var requestJson = $$"""{"is_official_mark_displayed":{{wireValue}},"viewer_id":"0","steam_id":0,"steam_session_ticket":""}""";
+        var response = await client.PostAsync("/profile/update_official_mark_display",
+            new StringContent(requestJson, Encoding.UTF8, "application/json"));
+
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var viewer = await db.Viewers.FirstAsync(v => v.Id == viewerId);
+        Assert.That(viewer.Info.IsOfficialMarkDisplayed, Is.EqualTo(expected));
+    }
+}