fix(api): graceful shutdown, единый обработчик ошибок и корректные 404

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

deploy/docker-compose.traefik.yml

@@ -54,6 +54,8 @@ services:
     pull_policy: always
     container_name: auth-portal
     restart: unless-stopped
+    init: true
+    stop_grace_period: 15s
     depends_on:
       - traefik
     # No host ports — only Traefik publishes 80/443.