refactor: replace custom CQRS/Kafka/Outbox infrastructure with Wolverine

[falberthen]

Replaces the hand-rolled messaging and CQRS infrastructure with WolverineFx 6.30. Same team as Marten, so the durable inbox/outbox reuses the Marten event store directly, without Debezium and Kafka Connect or a polling worker. The move also turns OrderSaga into a real Wolverine saga and lets tracing lean on Wolverine's native handler spans instead of manual plumbing.

Before	After
ICommandBus / IQueryBus + reflection dispatch	Wolverine conventional handler discovery
Confluent.Kafka consumer/producer + KafkaBackgroundWorker	Wolverine Kafka transport
Debezium + Kafka Connect CDC on mt_doc_outboxmessages	Wolverine durable inbox/outbox (Marten-backed)
Manual saga state handling	OrderSaga : Wolverine.Saga
ITraceable + TraceTaggingMiddleware + TelemetryTags	Wolverine handler spans + [Audit] on the message OrderId

Reason

The previous custom stack duplicated what Wolverine does natively and carried real operational weight: a Debezium connector, a Kafka Connect container, a polling background worker, and bespoke tracing middleware. Wolverine gives the same guarantees (durable, exactly-once-ish delivery, retries, dead letter, etc) with less code and a supported upgrade path.

Key changes

• Core loses CQRS/, EventBus/, Outbox/, Kafka/ abstractions. ICommand / IQuery survive as slim markers for CustomControllerBase overload resolution only. IntegrationEvent is now a pure marker.
• Each service registers Wolverine via AddCoreInfrastructure; the three broker participants (Order/Payment/Shipment) configure UseKafka with durable inbox/outbox in their Program.cs.
• Broker contracts carry [MessageIdentity(nameof(X))] so each bounded context's copy shares one wire name (and the name survives namespace moves).
• Service clients: Kiota clients register through AddHttpClient<T>, which Wolverine 6's codegen can't inline. UseServiceClientServiceLocation() (new, in EcommerceDDD.ServiceClients) whitelists exactly those client types.
• Observability: StronglyTypedId.ToString() added so [Audit] writes the bare id, so the SPA's Aspire deep-link (order.id) keeps working as before.