Fixes
- Register OidcAuthProvider with Jellyfin DI (fixes InvalidAuthProvider warnings on every request)
- Remove broken ChangePassword call from new user creation (crashed first-time OIDC logins)
- Fix MaxParentalRating defaulting to 0 (G-rated only) instead of null when unset in role mappings
- Add ServerId to credential storage so Jellyfin web correctly identifies the server after OIDC redirect
- Rename plugin to SSO-OIDC RBAC for clarity