Add Phase 2 OIDC howto set and update navigation - Howto-Google-OIDC.md: OAuth 2.0 client setup, consent screen, redirect URI, test login - Howto-GitHub-OIDC.md: GitHub OAuth App + Dex connector config, org/team restriction - Howto-Authelia-OIDC.md: Authelia native OIDC provider (vs Phase 1 forward-auth), group mapper, comparison table - Howto-Keycloak-OIDC.md: confidential client creation, group mapper, realm-path issuer note - Howto-Rotate-OIDC-secrets.md: per-IdP rotation steps, session secret distinction, verification - Howto-Recover-broken-OIDC.md: API key recovery, password fallback, debug log diagnosis, fix/remove provider - _Sidebar.md: Phase 2 OIDC section added - Home.md: Phase 2 OIDC howto table added