feat: simplified local-space and celestial, removed bubbles

apps/backend/Simulation/Model/SimulationWorld.cs

@@ -9,8 +9,7 @@ public sealed class SimulationWorld
     public required BalanceDefinition Balance { get; init; }
     public required List<SystemRuntime> Systems { get; init; }
     public required List<ResourceNodeRuntime> Nodes { get; init; }
-    public required List<NodeRuntime> SpatialNodes { get; init; }
-    public required List<LocalBubbleRuntime> LocalBubbles { get; init; }
+    public required List<CelestialRuntime> Celestials { get; init; }
     public required List<StationRuntime> Stations { get; init; }
     public required List<ShipRuntime> Ships { get; init; }
     public required List<FactionRuntime> Factions { get; init; }