fix(db-tool): prevent fd leak from logger to long-running daemons

The hectic logger opens fd 3 as a dup of stderr. Child processes inherit
this fd, and daemonized PostgreSQL/PostgREST keeping it open prevents the
terminal from returning to the prompt after the spawning script exits.

- Add with_closed_fds helper that runs commands in a subshell with fds
  3-9 redirected to /dev/null
- Inline the helper into both database and postgres-init builds
- Wrap pg_ctl start and postgrest with the helper

legacy/helper/posix-shell/log.sh

@@ -148,7 +148,7 @@ log() {
       ''
 
     # shellcheck disable=SC1003
-    fmt="$(printf "%s$delimetr" "$@" | sed 's/\\033\[0m/''\'"$color"'/g')"
+    fmt="$(printf "%s$delimetr" "$@" | sed 's/\\033\[0m/'\'"$color"'/g')"
     shift
     # shellcheck disable=SC1003
     printf "${BBLACK}${HECTIC_NAMESPACE}> %b\n" "$color$fmt$NC" >&3