refactor(网络同步): 重构实体同步逻辑和玩家生成流程

- 将EntityBase的health改为@export变量以便同步
- 添加MultiplayerSynchronizer节点处理网络同步
- 修改Wave.next()方法处理EncodedObjectAsID类型
- 添加findPlayer方法通过名称查找玩家
- 调整玩家生成流程，确保UIState.player正确设置

scripts/Contents/Panels/Starter.gd

@@ -63,6 +63,7 @@ func startMultiplayerGame():
 func startSingleplayerGame():
 	MultiplayerState.isMultiplayer = false
 	EntityBase.generatePlayer(playerNameInput.text)
+	UIState.player = EntityBase.findPlayer(playerNameInput.text)
 	WorldManager.rootNode.spawnWave()
 	UIState.closeCurrentPanel()