refactor(backend): align api namespaces and project name

apps/backend/Simulation/WorldService.cs

@@ -1,8 +1,10 @@
 using System.Threading.Channels;
 using Microsoft.Extensions.Options;
-using SpaceGame.Simulation.Api.Contracts;
+using SpaceGame.Api.Contracts;
+using SpaceGame.Api.Simulation.Engine;
+using SpaceGame.Api.Simulation.Model;
 
-namespace SpaceGame.Simulation.Api.Simulation;
+namespace SpaceGame.Api.Simulation;
 
 public sealed class WorldService(
   IWebHostEnvironment environment,
@@ -11,7 +13,7 @@ public sealed class WorldService(
 {
   private const int DeltaHistoryLimit = 256;
 
-  private readonly object _sync = new();
+  private readonly Lock _sync = new();
   private readonly OrbitalSimulationSnapshot _orbitalSimulation = new(orbitalSimulationOptions.Value.SimulatedSecondsPerRealSecond);
   private readonly ScenarioLoader _loader = new(environment.ContentRootPath, worldGenerationOptions.Value);
   private readonly SimulationEngine _engine = new(orbitalSimulationOptions.Value);