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。

Client/Assets/Scripts/DataCenter/DataCenter.LeadboardData.cs

@@ -2,9 +2,11 @@ using asap.core;
 using asap.playfab.async;
 using cfg;
 using game;
+using game.PlayerDataStorage;
 using PlayFab.ClientModels;
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Threading.Tasks;
 using tysdk;
@@ -162,6 +164,27 @@ namespace GameCore
             {
                 Statistics.Add(new StatisticUpdate() { StatisticName = names[i], Value = value[i] });
             }
+            if (userService is KVUserService kvUser)
+            {
+                var store = kvUser.SaveStore;
+                var writtenNames = new HashSet<string>(StringComparer.Ordinal);
+                bool accepted = false;
+                foreach (var statistic in Statistics)
+                {
+                    if (!writtenNames.Add(statistic.StatisticName)) continue;
+                    var write = store.Write(statistic.StatisticName, statistic.Value.ToString(CultureInfo.InvariantCulture));
+                    if (write.Accepted) accepted = true;
+                    else Debug.LogError("KV statistic write failed: " + statistic.StatisticName + ": " + write.Error);
+                }
+                if (accepted)
+                {
+                    var confirmation = await store.FlushAsync();
+                    if (confirmation.Status != PlayerSaveStatus.Confirmed)
+                        Debug.LogError("KV statistic save not confirmed: " + string.Join(",", writtenNames) +
+                            ": " + confirmation.Status + ": " + confirmation.Error);
+                }
+                return;
+            }
             UpdatePlayerStatisticsRequest request = new UpdatePlayerStatisticsRequest()
             {
                 Statistics = Statistics,