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/C2d修改前快照/000-EventDataRepository.cs.txt

@@ -0,0 +1,68 @@
+using System;
+using Newtonsoft.Json;
+using UnityEngine;
+
+namespace Activity.Data
+{
+    /// <summary>
+    /// 使用本次登录绑定的存档提供方，保留活动类型名作为存档键。
+    /// </summary>
+    public class EventDataRepository : IEventDataRepository
+    {
+        readonly game.PlayerDataStorage.IPlayerSaveStore store;
+        public EventDataRepository(game.PlayerDataStorage.IPlayerSaveStore store)
+        { this.store = store ?? throw new ArgumentNullException(nameof(store)); }
+        public void Save<T>(T data) where T : IEventData
+        {
+            if (data == null)
+            {
+                Debug.LogWarning($"[EventDataRepository] Cannot save null data for {typeof(T).Name}");
+                return;
+            }
+
+            try
+            {
+                var json = JsonConvert.SerializeObject(data);
+#if UNITY_EDITOR
+                Debug.Log($"[EventDataRepository] Saving {typeof(T).Name}: {json}");
+#endif
+                store.Write(typeof(T).Name, json).RequireAccepted();
+            }
+            catch (Exception e)
+            {
+                Debug.LogError($"[EventDataRepository] Failed to save {typeof(T).Name}: {e.Message}\n{e.StackTrace}");
+                throw;
+            }
+        }
+
+        public T Load<T>() where T : IEventData, new()
+        {
+            try
+            {
+                var read = store.Read(typeof(T).Name);
+                var dataStr = read.ValueOrThrow();
+                if (read.Found == false) return new T();
+                if (string.IsNullOrWhiteSpace(dataStr) || dataStr.Trim() == "null")
+                    throw new JsonSerializationException("Stored activity data cannot be empty or null.");
+// #if UNITY_EDITOR
+//                 Debug.Log($"[EventDataRepository] Load {typeof(T).Name}: {dataStr}");
+// #endif
+                var data = JsonConvert.DeserializeObject<T>(dataStr);
+                if (data == null) throw new JsonSerializationException("Stored activity data cannot be null.");
+                return data;
+            }
+            catch (Exception e)
+            {
+                Debug.LogError($"[EventDataRepository] Failed to load {typeof(T).Name}: {e.Message}\n{e.StackTrace}");
+                throw;
+            }
+        }
+
+        public bool Exists<T>() where T : IEventData
+        {
+            var read = store.Read(typeof(T).Name);
+            read.ValueOrThrow();
+            return read.Found.Value;
+        }
+    }
+}