feat: scene ghosting, as the client streams a zone's scenes

The client keeps the scene under the player loaded, the scenes the zone
file's transitions connect to it, and the global scene
(Zone::StreamScenesAroundPosition 0x0108a3f0, TerrainManager::GetSceneAtPos
0x01069010, the connected scenes at 0x01066500; transitions naming a
missing scene dropped as Zone::FixupInvalidTransitions 0x010842e0 does).

- ZoneScenes (dCommon): the terrain's scene map lookup and the scene graph,
  shared by the world server and the dashboard.
- Objects remember the scene they were placed in (spawners pass theirs on).
- ghosting_scenes=1 (world config, off by default): players get the objects
  of their loaded scenes instead of the ones within the ghosting distances;
  objects from no scene go by the scene under them. Zones without a scene
  map keep distance ghosting.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dGame/Entity.cpp

@@ -138,6 +138,7 @@ Entity::Entity(const LWOOBJID& objectID, const EntityInfo& info, User* parentUse
 	m_DefaultPosition = info.pos;
 	m_DefaultRotation = info.rot;
 	m_Scale = info.scale;
+	m_Scene = info.scene;
 	m_Spawner = info.spawner;
 	m_SpawnerID = info.spawnerID;
 	m_HasSpawnerNodeID = info.hasSpawnerNodeID;