Expand galaxy generation and viewer rendering

apps/backend/Simulation/RuntimeModels.cs

@@ -28,6 +28,7 @@ public sealed class ResourceNodeRuntime
   public required string Id { get; init; }
   public required string SystemId { get; init; }
   public required Vector3 Position { get; init; }
+  public required string SourceKind { get; init; }
   public required string ItemId { get; init; }
   public float OreRemaining { get; set; }
   public float MaxOre { get; init; }