fix(notification-service): add JWT_ACCESS_SECRET env var to docker-compose

notification-service was missing JWT_ACCESS_SECRET, causing it to use the
fallback 'dev-access-secret' instead of 'dev-access-secret-change-in-production'.
This made all auth-protected endpoints return 401, triggering logout in the app.

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

backend/docker-compose.yml

@@ -329,6 +329,7 @@ services:
       - KAFKA_BROKERS=kafka:9092
       - REDIS_HOST=redis
       - REDIS_PORT=6379
+      - JWT_ACCESS_SECRET=dev-access-secret-change-in-production
     depends_on:
       kafka:
         condition: service_healthy