chore: 同步 FishNet 脚本宏与 Unity 6000.6 序列化更新

- ProjectSettings.asset: Standalone 平台写入宏 FISHNET;FISHNET_V4（FishNet 的 ScriptingDefines 在编辑器加载时自动添加）

- QualitySettings.asset: 质量档序列化格式升级 serializedVersion 4 -> 5，新增 meshLodThreshold

- DefaultVolumeProfile.asset: URP Bloom 组件新增 filter 覆盖项

- DefaultPrefabObjects.asset: FishNet 自动生成的预制体注册表

ProjectSettings/QualitySettings.asset

@@ -6,7 +6,7 @@ QualitySettings:
   serializedVersion: 5
   m_CurrentQuality: 1
   m_QualitySettings:
-  - serializedVersion: 4
+  - serializedVersion: 5
     name: Mobile
     pixelLightCount: 2
     shadows: 2
@@ -34,6 +34,7 @@ QualitySettings:
     adaptiveVsyncExtraA: 0
     adaptiveVsyncExtraB: 0
     lodBias: 1
+    meshLodThreshold: 1
     maximumLODLevel: 0
     enableLODCrossFade: 1
     streamingMipmapsActive: 0
@@ -59,7 +60,7 @@ QualitySettings:
     terrainMaxTrees: 50
     excludedTargetPlatforms:
     - Standalone
-  - serializedVersion: 4
+  - serializedVersion: 5
     name: PC
     pixelLightCount: 2
     shadows: 2
@@ -87,6 +88,7 @@ QualitySettings:
     adaptiveVsyncExtraA: 0
     adaptiveVsyncExtraB: 0
     lodBias: 2
+    meshLodThreshold: 1
     maximumLODLevel: 0
     enableLODCrossFade: 1
     streamingMipmapsActive: 0