-- Migration 011: Timezone and Distributed Fire-Lock for Scheduled Workflows
-- Extends the scheduled_workflows table with:
--   timezone  — IANA timezone identifier for cron evaluation (e.g. "America/New_York")
--   locked_by — instance UUID holding the current fire lock (prevents double-fires)
--   locked_at — when the lock was acquired; TTL = 120 s is enforced in application code

DEFINE FIELD timezone  ON TABLE scheduled_workflows TYPE option<string>   DEFAULT NONE;
DEFINE FIELD locked_by ON TABLE scheduled_workflows TYPE option<string>   DEFAULT NONE;
DEFINE FIELD locked_at ON TABLE scheduled_workflows TYPE option<datetime> DEFAULT NONE;