C1: Arc<Mutex<EventStore>> changed from tokio::sync to std::sync + spawn_blocking
C2: StateMachine::transition merged into single lock scope
C3: Transaction boundaries (BEGIN/COMMIT) on all composite writes
M4: retry_count no longer overwritten by update_task_status
M5: RetryPolicy::handle_failure now atomic (single lock + transaction)
M6: Per-task timeout_seconds used in SQL instead of global config
M7: Explicit Priority::order() method instead of relying on variant order
M8: dequeue_and_assign uses CAS-style WHERE status='created' for atomicity