Session binding was bypassable: if the X-Session-Id header was absent,
validate_token skipped the check entirely, allowing a stolen JWT to be
used without the originating session.
Server-side: reject 401 early in Flask middleware and daemon WebSocket
handler when X-Session-Id is missing, before calling validate_token.
Updated validate_token to always enforce session_id matching for access
tokens (refresh tokens are unaffected as they carry no session_id claim).
Frontend: removed dead if (stored.session_id) guards in api.js since
the header is now always required. Added X-Session-Id to logout request
headers and always store session_id on login/refresh.
mteehan
b69ca330f4