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-C3c只读核查记录.json

@@ -0,0 +1,26 @@
+{
+  "date": "2026-09-30T14:58:43.4880340+08:00",
+  "type": "static-source-and-hash-audit",
+  "clientBaselineCount": 2122,
+  "c3bItems": 4,
+  "c3bEvidence": 8,
+  "failures": [],
+  "productionChanged": false,
+  "testsRun": false,
+  "formalRequests": 0,
+  "observations": [
+    "13 SDK operations and 2 retry wrappers; 4 shared SDK calls remain",
+    "Historical friend Level cannot replace LevelB without semantic mapping",
+    "Partner invitation directly reads nullable LastLogin.Value",
+    "SearchFriend is a reuse candidate, not proof of KV source"
+  ],
+  "arithmeticExample": {
+    "Level": 12,
+    "UiBuildingFromScore": 34,
+    "Building": 34,
+    "CorrectScore": 1200034,
+    "UiLevelFromScore": 12.0,
+    "UiLevelFromPlainLevel": 0.0,
+    "UiBuildingFromPlainLevel": 12
+  }
+}