Opening an expired or invalid link used to dump raw problem-details
JSON at the guest. Now they get a small page matching the sign-in
look, with the same neutral wording whether the link expired or never
existed (so tokens cannot be probed by outsiders), and an automatic
redirect to the Jellyfin home page. Fixes#1.
GuestHiddenSelectors now defaults to empty instead of shipping CSS
selectors for a plugin nobody else runs. Existing installs keep their
saved value. Fixes#3.