Swap the event transport

• Interface: EventBus (abstract class, publish(events): Promise<void>) in apps/worker/src/outbox/event-bus.ts.
• Today: BullMqEventBus copies each event into every queue whose filter in eventSubscribers (packages/jobs/src/queues.ts) accepts it, with jobId = event id. At least once, unordered.
• Bound in: apps/worker/src/outbox/outbox.module.ts.
• Env: none beyond REDIS_URL today.

Swap

1. A class extending EventBus that produces each EventEnvelope to one topic keyed by event.key (per-aggregate order), idempotently (the relay may republish a batch after a crash). Bind it in outbox.module.ts. The relay, emitEvent and every producer stay as they are.
2. Consumers are what move. Each is a BullMQ @Processor on an events-* queue today: events-audit (apps/worker/src/audit/audit.processor.ts), events-realtime (apps/worker/src/realtime/realtime.processor.ts), events-webhooks (apps/webhooks/src/outbound/fanout.processor.ts), events-notifications (apps/notifications/src/events/events.processor.ts), events-billing (apps/api/src/modules/billing/billing-events.processor.ts). Each becomes a consumer group applying its eventSubscribers filter itself, still deduping on the event id. Moving one consumer at a time works if the bus publishes to both for a while.
3. The broker's address in apps/worker/src/env.ts and each consumer's src/env.ts, .env.example, docs/environment.md; KEDA triggers in deploy/charts/stack change from queue length to consumer lag.

Tests

The outbox relay tests in apps/worker/test/worker.integration.test.ts, and each consumer's integration suite. A broker needs a local container for tests; add it to docker-compose.yml with a memory limit like the others.

Finish

1. The verify skill.
2. Ask the reviewer agent to review the change, and the security-reviewer agent: a new implementation brings its own credentials and sends data somewhere new. If you wrote a migration, the migration-reviewer agent too.
3. Update the seam's row in the README's "Scaling path" table if what's "Now" changed.