Change nebari user from UID 1001 to UID 1000

Replace the default ubuntu user (UID 1000) with the nebari user
running as UID 1000 instead of 1001. This ensures compatibility
with Kubernetes security contexts and volume permissions that
expect UID 1000.

Changes:
- Delete ubuntu user (UID 1000) from base image
- Create nebari user with UID 1000 (GID 100/users)
- Maintains non-root security posture
- Home directory: /home/nebari

Author: dcmcand

Dockerfile

@@ -51,7 +51,8 @@ FROM ubuntu:24.04@${UBUNTU_DIGEST} AS builder
 COPY --from=pixi-installer /usr/local/bin/pixi /usr/local/bin/pixi
 COPY scripts /opt/scripts
 
-RUN useradd -r -m -u 1001 -g 100 -s /bin/bash nebari && \
+RUN userdel -r ubuntu 2>/dev/null || true && \
+  useradd -m -u 1000 -g 100 -s /bin/bash nebari && \
   mkdir -p /opt/envs && \
   chown -R nebari:users /home/nebari /opt/envs