feat(tutorial): add /tutorial/gift_receive — grant + receipt + idempotent re-claim

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

SVSim.UnitTests/Infrastructure/SVSimTestFactory.cs

@@ -384,6 +384,18 @@ internal sealed class SVSimTestFactory : WebApplicationFactory<Program>
         return viewer.MissionData.TutorialState;
     }
 
+    /// <summary>
+    /// Reads the viewer's current currency balances from the DB. Used by gift_receive tests
+    /// to assert delta grants after claiming tutorial presents.
+    /// </summary>
+    public async Task<(ulong Crystals, ulong Rupees, ulong RedEther)> GetViewerCurrencyAsync(long viewerId)
+    {
+        using var scope = Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var viewer = await db.Viewers.FirstAsync(v => v.Id == viewerId);
+        return (viewer.Currency.Crystals, viewer.Currency.Rupees, viewer.Currency.RedEther);
+    }
+
     protected override void Dispose(bool disposing)
     {
         base.Dispose(disposing);