fix(09): IN-01 guard __resetDrainState against production use

apps/api/src/broker/outboxWorker.ts

@@ -881,6 +881,7 @@ export function stopOutboxTrigger(): void {
  * relying on the previous test having drained cleanly. Not for production use.
  */
 export function __resetDrainState(): void {
+  if (process.env.NODE_ENV === 'production') return; // test-only; never clear the guard in prod
   isDraining = false;
   drainRequested = false;
 }