Add a discovery preflight that reports the configured backup root, host
root, and snapshot directory counts before importing anything.
Show discovery status on host detail pages so missing mounts or mismatched
host directories are visible from the UI.
Warn clearly when discovery scans zero snapshots, including whether the
host backup directory is missing or simply empty.
Fix the global config edit view so default initial values are only used
when creating a new config, preventing saved backup_root values from
being hidden by form defaults.
Keep pobsync_home as an internal runtime setting instead of exposing it
in the normal Django setup form.
Mount a host backup directory into Docker at /backups and document
POBSYNC_BACKUP_ROOT so backup_root behaves predictably in containers.
Add a Django admin-backed management layer for pobsync configs, runs,
snapshots, and schedules. Keep the existing CLI engine as the execution
source of truth, add import/run management commands, and provide SQLite
default plus optional MariaDB Docker Compose support.
