Re-running install.sh was wiping BASEMENT_ADMIN_USER and _PASSWORD_HASH
back to empty in my-basement.xml — the user then had to re-enter them
in the Unraid UI every time. Annoying.
Template now declares those two fields as __PLACEHOLDER__ tokens.
install.sh, before fetching the new template, sed-extracts whatever's
currently in the existing my-basement.xml and feeds those values back
into the substitution. First-time installs sub to empty (user fills
via UI); subsequent runs preserve what's there.
Bcrypt's $-heavy chars survive sed because `|` is the delimiter and
sed only interprets $ in regex/match, not replacement.
matthew
574376aa75