fix(reward): add WALLET_SERVICE_URL to reward-service

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

backend/services/docker-compose.yml

@@ -318,6 +318,7 @@ services:
       # External Service URLs
       - REFERRAL_SERVICE_URL=http://rwa-referral-service:3004
       - AUTHORIZATION_SERVICE_URL=http://rwa-authorization-service:3009
+      - WALLET_SERVICE_URL=http://rwa-wallet-service:3001
     depends_on:
       postgres:
         condition: service_healthy