authorize-approval.js AUTO_APPROVERS direct-label bypass

Trap: allowing getsantry[bot] or sentry-release-bot[bot] through generic AUTO_APPROVERS authorization looks safe because both are approved automated requesters, but either could directly add accepted to the other’s request and bypass the Internal App’s request-bound proof. Fix: authorizeApproval() must fail closed for direct labels by both bots; only sentry-internal-app[bot] may represent automated approval, backed by the matching github-actions[bot] attestation. Cover both direct-bot paths with regressions.