Hiding .headerBackButton for guests also removed the video player's back
button (same class), so a guest could not return from playback to the
movie page. Stop hiding that class; keep home/drawer/search hidden.
Cast, studio, genre and tag links on the detail page now have
pointer-events disabled for guests so they stay visible but inert
(clicking Studio no longer spins on a page the guest cannot load), and
the add-to-playlist/add-to-collection actions are hidden.
Add a GuestHiddenSelectors config field (comma-separated CSS selectors,
surfaced through GuestState since guests cannot read plugin config) so
other plugins injected UI can be suppressed for guest sessions without
code changes; defaults to hiding the AI Search elements.
Includes fix for redemption failing with DbUpdateConcurrencyException:
change the guest password before applying the user policy, since
UpdatePolicyAsync bumps the user's EF concurrency token and a stale
instance then breaks ChangePassword.
Franciskid