5.0.0-JF12-beta

Jellyfin 12.0 (.NET 10) beta 5.0.0-JF12-beta (plugin version 5.0.0.28).
Install via the beta repository URL (a Jellyfin 12.0 server picks this build automatically by targetAbi):
https://raw.githubusercontent.com/iderex/jellyfin-plugin-sso/manifest-beta/manifest.json

Scope note (#743): the JF12/5.0 line is not validated against a live Jellyfin 12.0 server yet — no 12.0 GA server exists to run the E2E checklist against. It is CI-built and unit/conformance-tested only, and it is NOT part of the 4.x (Jellyfin 10.11) release-candidate gate; the 5.0 line clears its own live-validation gate when a Jellyfin 12.0 RC/GA build is available. Use these betas for testing, not production.

What's Changed

• Cover the back-channel logout discovery fail-closed branches by @iderex in #985
• Move internal docs local by @iderex in #988
• Slim the README to a lean start by @iderex in #989
• Strengthen the README AI-assistance disclosure by @iderex in #992
• Alert on failed scheduled publish + check manifest freshness by @iderex in #990
• Add a config-page screenshot to the README by @iderex in #993
• Remove the README config screenshot; fix stale internal-doc links by @iderex in #994
• Promote to Release Candidate by @iderex in #996
• Add a served-surface string localizer with the English baseline catalog [#913] by @iderex in #997
• Resolve the served-page culture from Accept-Language [#913] by @iderex in #998
• Localize the auth-completion page chrome [#913] by @iderex in #999
• Localize the login rejection messages on the browser error page [#913] by @iderex in #1000
• Add client-side UI localization and wire the linking page [#913] by @iderex in #1001
• Localize the configuration page chrome [#913] by @iderex in #1002

Full Changelog: 4.3.0-beta.13...5.0.0-JF12-beta.28