Switch to a non-root user to avoid permission issues at runtime

Dockerfile

@@ -10,8 +10,15 @@ ENV LIVEBOOK_DATA_PATH "/data"
 ENV LIVEBOOK_PORT 7860
 
 EXPOSE 7860
-USER root
-COPY public-apps/ /public-apps
+
 RUN mkdir -p /data
 RUN chmod 777 /data
+
+# The Space container runs with user ID 1000
+RUN useradd -m -u 1000 user
+ENV HOME=/home/user
+
+USER user
+
+COPY --chown=user public-apps/ /public-apps
 RUN /app/bin/warmup_apps