백엔드 도커파일 수정

docker/prod/backend.Dockerfile

@@ -4,9 +4,9 @@
 FROM node:20-bookworm-slim AS base
 WORKDIR /app
 ENV NODE_ENV=production
-# Install OpenSSL and required certs
+# Install OpenSSL, curl (for healthcheck), and required certs
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends openssl ca-certificates \
+    && apt-get install -y --no-install-recommends openssl ca-certificates curl \
     && rm -rf /var/lib/apt/lists/*
 
 # Dependencies stage (install deps and generate Prisma client)