repo(viewer): add UDID lookup, anonymous register, Steam link helpers

Extracts the default-loadout body into a private BuildDefaultViewer
helper shared by the existing Steam-import path and a new
RegisterAnonymousViewer for /tool/signup. LinkSteamToViewer is the
seam SteamSessionAuthenticationHandler will call on first-Steam-touch
of a UDID-keyed viewer.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.UnitTests/Repositories/ViewerRepositoryTests.cs

@@ -71,4 +71,99 @@ public class ViewerRepositoryTests
         Assert.That(viewer.LeaderSkins, Is.Not.Empty,
             "Viewer should own at least one leader skin from class defaults.");
     }
+
+    [Test]
+    public async Task RegisterAnonymousViewer_creates_viewer_with_udid_and_no_socials()
+    {
+        using var factory = new SVSimTestFactory();
+        var udid = Guid.NewGuid();
+
+        long viewerId;
+        using (var scope = factory.Services.CreateScope())
+        {
+            var repo = scope.ServiceProvider.GetRequiredService<IViewerRepository>();
+            var v = await repo.RegisterAnonymousViewer(udid);
+            viewerId = v.Id;
+        }
+
+        using var verifyScope = factory.Services.CreateScope();
+        var db = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var loaded = await db.Viewers
+            .Include(v => v.Classes)
+            .Include(v => v.SocialAccountConnections)
+            .FirstAsync(v => v.Id == viewerId);
+
+        Assert.That(loaded.Udid, Is.EqualTo(udid));
+        Assert.That(loaded.SocialAccountConnections, Is.Empty);
+        Assert.That(loaded.Classes, Is.Not.Empty,
+            "Default-loadout body should populate Classes (smoke-test the shared BuildDefaultViewer helper).");
+    }
+
+    [Test]
+    public async Task RegisterAnonymousViewer_with_empty_udid_throws()
+    {
+        using var factory = new SVSimTestFactory();
+        using var scope = factory.Services.CreateScope();
+        var repo = scope.ServiceProvider.GetRequiredService<IViewerRepository>();
+
+        Assert.ThrowsAsync<InvalidOperationException>(async () =>
+            await repo.RegisterAnonymousViewer(Guid.Empty));
+    }
+
+    [Test]
+    public async Task GetViewerByUdid_returns_viewer_or_null()
+    {
+        using var factory = new SVSimTestFactory();
+        var udid = Guid.NewGuid();
+
+        long createdId;
+        using (var scope = factory.Services.CreateScope())
+        {
+            var repo = scope.ServiceProvider.GetRequiredService<IViewerRepository>();
+            createdId = (await repo.RegisterAnonymousViewer(udid)).Id;
+        }
+
+        using (var scope = factory.Services.CreateScope())
+        {
+            var repo = scope.ServiceProvider.GetRequiredService<IViewerRepository>();
+            var hit = await repo.GetViewerByUdid(udid);
+            var miss = await repo.GetViewerByUdid(Guid.NewGuid());
+
+            Assert.That(hit, Is.Not.Null);
+            Assert.That(hit!.Id, Is.EqualTo(createdId));
+            Assert.That(miss, Is.Null);
+        }
+    }
+
+    [Test]
+    public async Task LinkSteamToViewer_appends_steam_social_connection()
+    {
+        using var factory = new SVSimTestFactory();
+        var udid = Guid.NewGuid();
+        const ulong steamId = 76_561_198_900_000_001UL;
+
+        long viewerId;
+        using (var scope = factory.Services.CreateScope())
+        {
+            var repo = scope.ServiceProvider.GetRequiredService<IViewerRepository>();
+            viewerId = (await repo.RegisterAnonymousViewer(udid)).Id;
+        }
+
+        using (var scope = factory.Services.CreateScope())
+        {
+            var repo = scope.ServiceProvider.GetRequiredService<IViewerRepository>();
+            await repo.LinkSteamToViewer(viewerId, steamId);
+        }
+
+        using var verifyScope = factory.Services.CreateScope();
+        var db = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var loaded = await db.Viewers
+            .Include(v => v.SocialAccountConnections)
+            .FirstAsync(v => v.Id == viewerId);
+
+        Assert.That(loaded.SocialAccountConnections, Has.Count.EqualTo(1));
+        Assert.That(loaded.SocialAccountConnections[0].AccountType,
+            Is.EqualTo(SocialAccountType.Steam));
+        Assert.That(loaded.SocialAccountConnections[0].AccountId, Is.EqualTo(steamId));
+    }
 }