feat(upserver): 保存M2客户端KV迁移至本人统计写检查点

保存独立KV用户服务、固定会话存档与原业务接线，以及C3d资料缓存和C3e本人统计写。
保留原PF/AGG路线、业务公式和时序；榜单读取、好友资料、公告、匹配及首场景闸仍待完成。

验证：ServiceHost两条件各33组646断言；Unity CLI Loop编译0错误269警告。
包含相关方案、评审裁决、测试及状态文档。未操作服务器、正式账号或打包。

CodexOutput/upserver/B3BatchMigration/M2/M2-CP2A-受审基线变化范围核验.json

@@ -0,0 +1,21 @@
+{
+  "baselineItems": 37,
+  "unchanged": 26,
+  "changed": [
+    "Client/Assets/Scripts/AOTScripts/Boostrap.cs",
+    "Client/Assets/Scripts/SubBoostrap.cs",
+    "Client/Assets/Scripts/Core/CustomServerMgr.cs",
+    "Client/Assets/Scripts/Services/UserService.cs",
+    "Client/Assets/Scripts/Services/UserService.KVLoad.cs",
+    "Client/Assets/Scripts/Services/PlayerData/PlayerKVGameLoadCoordinator.cs",
+    "Client/Assets/Scripts/Services/PlayerData/PlayerKVLoginContext.cs",
+    "Client/Assets/Scripts/Services/PlayerData/PlayerKVControlledLoadCapability.cs",
+    "Client/Assets/Scripts/Services/PlayerData/PlayerKVGameplayBindings.cs",
+    "Client/Assets/Scripts/Stages/LoginStage.cs",
+    "Client/Assets/Scripts/Stages/PFLoginAct.cs"
+  ],
+  "changedCount": 11,
+  "changedOutsideApprovedProduction": [],
+  "newApprovedSource": "Client/Assets/Scripts/Services/PlayerData/PlayerKVRuntimeSelection.cs",
+  "approvedProductionScopeMatched": true
+}