Refactor backend into domain-first slices

apps/backend/Universe/Api/ResetWorldHandler.cs

@@ -0,0 +1,15 @@
+using FastEndpoints;
+
+namespace SpaceGame.Api.Universe.Api;
+
+public sealed class ResetWorldHandler(WorldService worldService) : EndpointWithoutRequest
+{
+  public override void Configure()
+  {
+    Post("/api/world/reset");
+    AllowAnonymous();
+  }
+
+  public override Task HandleAsync(CancellationToken cancellationToken) =>
+    SendOkAsync(worldService.Reset(), cancellationToken);
+}