appExternalUrl is injected as OIDC_AUTH_EXTERNAL_URL (the redirect URI base); Authelia rejects non-https redirect URIs in production. Added .refine() guard matching the existing oidcIssuer pattern. Added test that verifies http:// appExternalUrl is rejected with 400. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>