The previous entrypoint script used 'set -euo pipefail', which caused runtime errors
because /bin/sh (Dash/BusyBox) does not support 'pipefail'. This commit makes the
entrypoint fully POSIX-safe, adds robust fallbacks for missing scripts, and improves
logging. Also removes a trailing newline in the navigator Docker Compose template.
Related ChatGPT discussion: https://chatgpt.com/share/68eab0b7-7a64-800f-a8aa-e7d7262a262e