fix(trading-service): 修复P2P转账API响应双重包装问题

- 移除controller中的手动包装，由TransformInterceptor统一处理
- 前端增加类型检查防止解析错误

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/trading-service/src/api/controllers/p2p-transfer.controller.ts

@@ -45,7 +45,8 @@ export class P2pTransferController {
       token,
     );
 
-    return { success: true, data: result };
+    // TransformInterceptor 会自动包装成 { success: true, data: ... }
+    return result;
   }
 
   @Get('transfers/:accountSequence')
@@ -71,6 +72,7 @@ export class P2pTransferController {
       pageSize ?? 20,
     );
 
-    return { success: true, data: result.data };
+    // TransformInterceptor 会自动包装成 { success: true, data: ... }
+    return result.data;
   }
 }

frontend/mining-app/lib/data/datasources/remote/trading_remote_datasource.dart

@@ -398,7 +398,7 @@ class TradingRemoteDataSourceImpl implements TradingRemoteDataSource {
       final response = await client.get(
         ApiEndpoints.p2pTransferHistory(accountSequence),
       );
-      final List<dynamic> data = response.data;
+      final List<dynamic> data = response.data is List ? response.data : [];
       return data.map((json) => P2pTransferModel.fromJson(json)).toList();
     } catch (e) {
       throw ServerException(e.toString());