Remove apt-get/curl dependency from Docker healthcheck

Use Python urllib instead of curl for the container healthcheck to
avoid needing apt-get install during image build (was hitting disk
space issues on the build host).

Dockerfile

@@ -4,10 +4,6 @@ FROM python:3.11-slim AS base
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1
 
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    && rm -rf /var/lib/apt/lists/*
-
 RUN groupadd -r iobj && useradd -r -g iobj -m iobj
 WORKDIR /app
 RUN mkdir -p /app/data && chown -R iobj:iobj /app
@@ -26,9 +22,10 @@ USER iobj
 
 ENV IOBJ_DATA_DIR=/app/data
 
-# Health check — dynamic port support for Nomad
+# Health check — dynamic port support for Nomad (no curl/apt-get needed)
 HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
-    CMD curl -f http://localhost:${PORT:-8000}/health || exit 1
+    CMD python -c "import os,urllib.request,sys; \
+    urllib.request.urlopen(f'http://localhost:{os.environ.get(\"PORT\",\"8000\")}/health', timeout=5)" || exit 1
 
 EXPOSE 8000