fix: forward RATE_LIMIT_RPM and MAX_FILE_SIZE_MB to backend container

These env vars were set in the CI workflow step but never passed through
docker-compose to the container, so the backend always used defaults
(100 RPM), causing 429 errors in E2E tests.

docker-compose.yml

@@ -12,6 +12,8 @@ services:
       CORS_ORIGINS: ${CORS_ORIGINS:-http://localhost:3000,http://localhost:5173}
       DOCLING_SERVE_URL: ${DOCLING_SERVE_URL:-}
       DOCLING_SERVE_API_KEY: ${DOCLING_SERVE_API_KEY:-}
+      RATE_LIMIT_RPM: ${RATE_LIMIT_RPM:-100}
+      MAX_FILE_SIZE_MB: ${MAX_FILE_SIZE_MB:-50}
     deploy:
       resources:
         limits: