saveMeeting/loadMeeting/deleteMeeting built path.join(meetingsDir, id +
'.json') straight from req.params.id, so an admin-authed :id like
'../../etc/passwd' could read/write/delete outside internal-meetings/.
Centralize a meetingPath() helper that strips anything outside
[A-Za-z0-9_-] (mirrors output-store.js) and throws on an empty result;
load/delete catch it as 404/no-op. Add a regression test.
Keysat