fix setup wizard: runtime crash, SSH mismatch, HTTPS fallback

- remove `local` keyword outside function (runtime crash with set -e)
- stop auto-constructing mirror URL when SSH-detected user doesn't
  match explicit personal username (wrong SSH key pairing)
- confirm SSH-detected account when personal username is blank
- add SSH-to-HTTPS fallback in test_push_access when SSH key can't
  reach the mirror repo (work-only laptop scenario)
- restore original SSH remote if HTTPS auth fails
- add prompt_mirror_url, test_push_access, verify_mirror_owner,
  parse_remote_owner helpers
- centralize push verification and owner checks

Author: yuvrajangadsingh