fix(compose): limit frontend memory to 64m

On Jambotron the project memory budget is split equally between services
without their own limit, so nginx got 341 MB while the backend was at 80%
of its share. With 64m for the frontend the backend and the database get
about 480 MB each.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docker-compose.yml

@@ -48,6 +48,9 @@ services:
         condition: service_healthy
     ports:
       - "8081:80"
+    # nginx со статикой хватает 64 МБ. На Jambotron бюджет памяти проекта делится поровну между
+    # сервисами без своего лимита — так backend и база получат больше
+    mem_limit: 64m
     networks:
       - demo-decoupled