Extend the runtime self check with native install diagnostics for the
environment file, service user, backup root ownership, and SQLite database
path. Export install metadata from the systemd units and pobsync-manage wrapper
so custom env files and service users are visible to Django checks.
Document restart, journal log inspection, and rollback steps in the README so
production updates have a clear recovery path.
Add a pobsync-manage wrapper that loads the native environment file before
running Django management commands, so production commands use the same
database and runtime settings as the systemd services.
Install the wrapper from the systemd installer, use it for migrations,
static collection, SSH key setup, and superuser creation, and document it
in the README for operational commands.
