fix: use openssl passwd instead of chpasswd for user creation

chpasswd fails with PAM error in Docker build. Use useradd -p with
openssl passwd -6 to set password directly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -36,8 +36,7 @@ RUN dpkg-query -W -f='${Package}\n' | sort > /etc/base-packages.list
 RUN ssh-keygen -A
 
 # User account (for SSH login); container runs as root for system persistence
-RUN (useradd -m -u 1000 -s /bin/bash user 2>/dev/null) || true
-RUN echo "user:huggingrun" | chpasswd
+RUN useradd -m -u 1000 -s /bin/bash -p "$(openssl passwd -6 huggingrun)" user 2>/dev/null || true
 RUN mkdir -p /data && chown 1000:1000 /data
 
 # nginx + bridge + startup scripts