fix(mining-admin): use outbox_id for event idempotency key

The outbox_events table uses outbox_id as the primary key column name
(mapped from id in Prisma). When Debezium captures changes, the message
contains outbox_id field, not id. This caused all events to have
undefined eventId, resulting in duplicate detection treating all events
as duplicates after the first one.

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

backend/services/mining-admin-service/src/infrastructure/kafka/cdc-consumer.service.ts

@@ -324,12 +324,18 @@ export class CdcConsumerService implements OnModuleInit, OnModuleDestroy {
 
     // Debezium outbox 格式转换
     // 原始格式：{ event_type, aggregate_type, aggregate_id, payload (JSON string), ... }
+    // 注意：不同服务的 outbox 表主键列名可能不同：
+    // - contribution-service: outbox_id (mapped from id in Prisma)
+    // - 其他服务可能使用: id
     const payload = typeof data.payload === 'string'
       ? JSON.parse(data.payload)
       : data.payload;
 
+    // 优先使用 outbox_id（contribution-service），回退到 id
+    const eventId = data.outbox_id ?? data.id;
+
     return {
-      id: String(data.id),
+      id: String(eventId),
       eventType: data.event_type,
       aggregateType: data.aggregate_type,
       aggregateId: data.aggregate_id,