/api/backups returned plain filename strings while pages/backups.html's
server-rendered dots came from get_local_backups_with_status()/
get_vm_backups_with_status(). platform.js's DOMContentLoaded handler always
calls refreshBackupsList() (backups.html has #backup-history-list, which
triggers it unconditionally), which re-fetches /api/backups and rebuilds
#local-backup-list/#vm-backup-list via renderBackupList() — a version with
zero knowledge of status, wiping out the dots seconds after initial paint.
Switch /api/backups to the *_with_status() variants and have
renderBackupList() render the same status-dot markup as the Jinja template,
so the dot is sourced from persisted backup metadata on every render path,
not just the first one.
