conf_cache_save.sh runs first on array stop — snapshots partner confs from RAM
cache to /boot/config/varaverk/conf_bak/ before anything else shuts down.
conf_cache_restore.sh runs after conf_sync.sh on array start — if partner was
unreachable and RAM cache is incomplete, loads the backup into RAM then removes
it. Normal reboots: backup written, fresh pull succeeds, backup deleted unused.
Edge case (partner down at boot): backup fills the gap so fallback.sh has the
partner vars it needs to operate correctly.
