* install: answer every prompt from the environment, survive a closed stdin
Every interactive prompt takes a var_<app>_<name> override and treats a
closed stdin like Enter (`|| true`), so an install keeps going after the
console that started it is gone. Values the script cannot do without end
with exit 64 and name the variable to set. Validation loops stop asking
when nobody can answer instead of spinning on an empty read.
* mongodb, paperless-gpt: accept yes as well as y