fix(docker): 为contribution-service添加JWT_SECRET配置

contribution-service需要JWT_SECRET来验证auth-service签发的token。
与auth-service共享相同的密钥配置。

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

backend/services/docker-compose.2.0.yml

@@ -44,6 +44,8 @@ services:
       # 推荐关系 (referral-service)
       CDC_TOPIC_REFERRALS: ${CDC_TOPIC_REFERRALS:-cdc.referral.public.referral_relationships}
       CDC_CONSUMER_GROUP: contribution-service-cdc-group
+      # JWT 配置 (与 auth-service 共享密钥以验证 token)
+      JWT_SECRET: ${JWT_SECRET:-your-jwt-secret-change-in-production}
     ports:
       - "3020:3020"
     healthcheck: