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.h

@@ -349,6 +349,9 @@ public:
 	// Scale will only be communicated to the client when the construction packet is sent
 	void SetScale(const float scale) { m_Scale = scale; };
 
+	// The zone scene the object was placed in (EntityInfo::scene), -1 when it came from none
+	int32_t GetScene() const { return m_Scene; }
+
 	void RegisterMsg(const MessageType::Game msgId, std::function<bool(GameMessages::GameMsg&)> handler);
 
 	bool HandleMsg(GameMessages::GameMsg& msg) const;
@@ -392,6 +395,7 @@ private:
 	NiPoint3 m_DefaultPosition;
 	NiQuaternion m_DefaultRotation = QuatUtils::IDENTITY;
 	float m_Scale;
+	int32_t m_Scene = -1;
 
 	Spawner* m_Spawner;
 	LWOOBJID m_SpawnerID;