ed2b9e43c8
The pre-update / pre-migration backup path (_write_full_zip_backup) had the same /tmp staging bug as run_backup: a small tmpfs at the default tempfile location silently drops large *.db files from the archive. Route its SQLite staging temp files to the output zip's directory as well, and add regression tests (mutation-verified) for both staging paths. Co-authored-by: liuhao1024 <sunsky.lau@gmail.com>