fix(reporting): 修复 contract.signed 事件 BigInt(undefined) 错误

根因：planting-service 发送的 contract.signed 消息为嵌套结构
  { eventName: 'contract.signed', data: { orderNo, userId, ... } }
但 reporting-service handleContractSigned 按扁平结构解析
  message.userId → undefined → BigInt(undefined) → TypeError
导致 ~200 次/10分钟持续报错。

修复：
- 消息类型改为匹配实际嵌套格式 { eventName, data: { ... } }
- 解构 message.data 后再访问各字段
- 添加 userId 防御性检查，避免再次 BigInt 崩溃
- 与 referral-service ContractSigningHandler 消息结构保持一致

影响范围：仅 reporting-service 活动记录，不影响核心业务流程
(referral-service / reward-service 已正确处理嵌套格式)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/services/reporting-service/src/infrastructure/kafka/activity-event-consumer.controller.ts

@@ -637,47 +637,64 @@ export class ActivityEventConsumerController {
   /**
    * 监听合同签署事件 (planting-service)
    * Topic: contract.signed
+   *
+   * 消息格式（由 planting-service EventPublisherService.publishContractSigned 发送）:
+   *   { eventName: 'contract.signed', data: { orderNo, userId, accountSequence, ... } }
+   *
+   * 注意：实际 payload 嵌套在 data 字段下，与 referral-service ContractSigningHandler 一致。
+   * 之前误用扁平结构导致 message.userId 为 undefined → BigInt(undefined) 抛出
+   * TypeError (~200次/10分钟)。
    */
   @MessagePattern('contract.signed')
   async handleContractSigned(
     @Payload()
     message: {
-      orderNo: string;
-      userId: string;
-      accountSequence: string;
-      treeCount: number;
-      totalAmount: number;
-      provinceCode: string;
-      cityCode: string;
-      signedAt: string;
+      eventName: string;
+      data: {
+        orderNo: string;
+        userId: string;
+        accountSequence: string;
+        treeCount: number;
+        totalAmount: number;
+        provinceCode: string;
+        cityCode: string;
+        signedAt?: string;
+      };
     },
   ) {
-    this.logger.log(`Received contract.signed event: ${message.orderNo}`);
+    const eventData = message.data;
+
+    if (!eventData?.userId) {
+      this.logger.warn(`Received contract.signed with missing data.userId, skipping. Raw: ${JSON.stringify(message)}`);
+      return;
+    }
+
+    this.logger.log(`Received contract.signed event: ${eventData.orderNo}`);
 
     try {
       const created = await this.activityRepo.createIfNotExists({
         activityType: 'contract_signed' as ActivityType,
         title: '合同签署',
-        description: `用户签署了 ${message.treeCount} 棵榴莲树认种合同`,
+        description: `用户签署了 ${eventData.treeCount} 棵榴莲树认种合同`,
         icon: '📝',
-        relatedUserId: BigInt(message.userId),
+        relatedUserId: BigInt(eventData.userId),
         relatedEntityType: 'contract',
-        relatedEntityId: message.orderNo,
+        relatedEntityId: eventData.orderNo,
         metadata: {
-          orderNo: message.orderNo,
-          accountSequence: message.accountSequence,
-          treeCount: message.treeCount,
-          totalAmount: message.totalAmount,
-          provinceCode: message.provinceCode,
-          cityCode: message.cityCode,
-          signedAt: message.signedAt,
+          orderNo: eventData.orderNo,
+          accountSequence: eventData.accountSequence,
+          treeCount: eventData.treeCount,
+          totalAmount: eventData.totalAmount,
+          provinceCode: eventData.provinceCode,
+          cityCode: eventData.cityCode,
+          signedAt: eventData.signedAt,
         },
       });
 
       if (created) {
-        this.logger.log(`Activity recorded for contract signing: ${message.orderNo}`);
+        this.logger.log(`Activity recorded for contract signing: ${eventData.orderNo}`);
       } else {
-        this.logger.log(`Skipped duplicate contract signing event: ${message.orderNo}`);
+        this.logger.log(`Skipped duplicate contract signing event: ${eventData.orderNo}`);
       }
     } catch (error) {
       this.logger.error(`Error recording contract signing activity:`, error);