Implement OIDC Back-Channel Logout 1.0 (RFC). When enabled, the IdP can
POST a signed logout_token JWT to invalidate user sessions server-side.
- Add BackchannelLogoutHandler: JWT verification via jose, jti replay
protection with bounded cache, session destruction by sub or sid
- Add oidcSessionId column to sessions table with index for fast lookups
- Add backchannel logout route (POST /auth/openid/backchannel-logout)
- Notify connected clients via socket to redirect to login page
- Add authOpenIDBackchannelLogoutEnabled toggle in schema-driven settings UI
- Migration v2.34.0 adds oidcSessionId column and index
- Polish settings UI: auto-populate loading state, subfolder dropdown
options, KeyValueEditor fixes, localized descriptions via descriptionKey,
duplicate key detection, success/error toasts
- Localize backchannel logout toast (ToastSessionEndedByProvider)
- OidcAuthStrategy tests now use real class via require-cache stubbing
