fix: 将时间戳转换为本地时区并添加调试日志

在AgentController和MessageModel中将时间戳转换为本地时区
在iOS和Android的ChatStorageHelper中添加调试日志以便追踪历史记录读取

lib/data/models/message_model.dart

@@ -34,7 +34,7 @@ class Message {
       sessionid: json['sessionid'] as String, // 会话ID
       isUser: json['isUser'] as bool,
       text: json['text'] as String,
-      timestamp: DateTime.parse(json['timestamp'] as String),
+      timestamp: DateTime.parse(json['timestamp'] as String).toLocal(),
       isRecognizing: json['isRecognizing'] as bool? ?? false,
       hasImage: json['hasImage'] as bool? ?? false,
       imagePath: json['imagePath'] as String?,

lib/modules/agent/controllers/agent_controller.dart

@@ -496,7 +496,7 @@ class AgentController extends GetxController with WidgetsBindingObserver {
         isUser: msg.sender == 'user',
         text: msg.message,
         meta: meta,
-        timestamp: DateTime.parse(msg.timestamp),
+        timestamp: DateTime.parse(msg.timestamp).toLocal(),
         hasImage: hasImage,
         imagePath: imagePath,
       );

local_plugins/chat_storage/android/src/main/kotlin/com/yunqiinnovation/chat_storage/ChatStorageHelper.kt

@@ -295,6 +295,9 @@ class ChatStorageHelper(context: Context) {
         val metadataIndex = cursor.getColumnIndex(ChatDatabaseHelper.COLUMN_METADATA)
         
         while (cursor.moveToNext()) {
+            val timestamp = cursor.getString(timestampIndex)  // 👈 提前取出 timestamp
+            Log.d(TAG, "getMessages: 读取历史记录: $timestamp")  // 👈 与 iOS 对齐的 log
+
             val jsonObject = JSONObject().apply {
                 put("id", cursor.getInt(idIndex))
                 put("agentId", cursor.getString(agentIdIndex))

local_plugins/chat_storage/ios/chat_storage/Sources/chat_storage/ChatStorageHelper.swift

@@ -175,6 +175,7 @@ public class ChatStorageHelper {
                 let date = Date(timeIntervalSince1970: TimeInterval(createdAt))
                 let formatter = ISO8601DateFormatter()
                 let timestamp = formatter.string(from: date)
+                os_log("getMessages: 读取历史记录: %{public}@", log: logger, type: .info, timestamp)
                 
                 var messageDict: [String: Any] = [
                     "id": id,