Show Docker-style per-mirror progress in the wizard

Replace the single "Creating N mirror(s)…" spinner with one live line per (repo, region), each updating independently as its CreateMirror + clone poll advance (processing → ready), then the existing summary table. Lines read "owner/repo @ <cluster-host> <spinner|✓|✗> <status>". A per-poll status callback now flows through awaitMirrorReady/createAndAwaitMirror (one-shot passes nil and keeps its single spinner). Non-TTY degrades to one printed line per mirror as it finalizes.