Harden backup integrity, implement verified restore and safe upgrades

tests/run.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+cd "$(dirname "$0")/.."
+for script in lib/common.sh usr-local-sbin/*.sh install.sh tests/run.sh; do bash -n "$script"; done
+shellcheck -x lib/common.sh usr-local-sbin/*.sh install.sh tests/run.sh
+python3 -m unittest discover -s tests -v