incus-copy.sh: add -r <src-remote> (pull all of a remote's instances to
the local host) and -p <dest-project> (copy local instances into another
local project/pool, for the on-host backup leg on a second disk). Copy
all instances instead of only running ones, abort cleanly if the
instance list fails, and keep boot.autostart=false on every replica.
incus-backup.sh: add a local destination mode (-d local, now the
default) that writes dumps/rsyncs straight to the backup root without
ssh; add -b to override the /backup root, flock against overlapping
runs, set -u, non-zero exit when any step fails, and fix the invalid
`incus exec -n` flag that made MariaDB dumps fail on modern incus.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>