refactor(game): 重构游戏云端数据同步逻辑

1. 新增微信云函数双向同步接口，将时间戳对比逻辑移至云端完成
2. 简化初始化流程，合并云端登录与数据同步步骤
3. 重构GameDataSync类，统一同步流程并改为异步调用
4. 替换旧的getCloudData接口为新的syncFromCloud方法

build-templates/wechatgame/cloud_functions/cocos_cloud/index.js

@@ -48,6 +48,53 @@ exports.main = async (event, context) => {
         msg: `Save fail, ${JSON.stringify(saveDataRes)}`
       };
     }
+  } else if (cmd === "sync") {
+    // 双向同步：比较客户端与云端时间戳，新的一方覆盖另一方
+    let clientData = event.data || {};
+    let user = await getOrCreaterUser(db, wxContext.OPENID);
+    if (!user) {
+      return { code: -1, msg: "Get or create user fail" };
+    }
+
+    let cloudData = user.game_data || {};
+    let clientTs = clientData.timestamp || 0;
+    let cloudTs = cloudData.timestamp || 0;
+
+    if (clientTs > cloudTs) {
+      // 客户端较新：写入云端
+      let saveDataRes = await db.collection(user_db_name).doc(user._id).update({
+        data: {
+          game_data: _.set(clientData)
+        }
+      });
+      console.log("Sync: client newer, saved to cloud:", saveDataRes, clientData);
+      if (saveDataRes?.stats?.updated >= 1) {
+        return {
+          code: 200,
+          updated: true, // 云端已被客户端数据覆盖
+          data: {
+            openid: wxContext.OPENID,
+            game_data: clientData
+          }
+        };
+      } else {
+        return {
+          code: -1,
+          msg: `Sync save fail, ${JSON.stringify(saveDataRes)}`
+        };
+      }
+    } else {
+      // 云端较新或一致：下发云端数据
+      console.log("Sync: cloud newer, return cloud data");
+      return {
+        code: 200,
+        updated: false, // 客户端应使用云端数据
+        data: {
+          openid: wxContext.OPENID,
+          game_data: cloudData
+        }
+      };
+    }
   }
 
   return {