Keep curl in Docker image for healthcheck

Curl was installed to download Node.js setup script then purged.
Coolify needs it for HTTP health checks inside the container.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -37,7 +37,6 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
       curl ca-certificates \
  && curl -fsSL https://deb.nodesource.com/setup_20.x | bash - \
  && apt-get install -y --no-install-recommends nodejs \
- && apt-get purge -y curl \
  && rm -rf /var/lib/apt/lists/*
 
 ENV NODE_ENV=production