refactor: migrate eventsourced to codeberg and go-messaging-amqp

Move eventsourced modules from gitlab.com/unboundsoftware to codeberg.org/eventsourced.
The Codeberg amqp publisher is built on go-messaging-amqp, so the service
switches from sparetimecoders/goamqp as well:

- routing keys are mapped on the eventsourced publisher (newEventPublisher)
- cache consumers are typed handlers; Cache.Update drops the goamqp shape
- publishes detach from the request context (uncancelledPublisher)
- closeEvents is buffered and the receiver also watches rootCtx
- WithPrefetchLimit dropped (no-op, 20 is the default)
- amqp091-go v1.15.0 (GO-2026-6372)
- renovate groups codeberg.org/messaging with eventsourced

Only transient consumer queues are used, so no queue cutover is needed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Dpb7Y47dPz246oY9bCzh7k

CLAUDE.md

@@ -9,7 +9,7 @@ This is a GraphQL schema registry service that manages federated GraphQL schemas
 ## Architecture
 
 ### Event Sourcing
-The system uses event sourcing via `gitlab.com/unboundsoftware/eventsourced`. Key domain aggregates are:
+The system uses event sourcing via `codeberg.org/eventsourced`. Key domain aggregates are:
 - **Organization** (domain/aggregates.go): Manages organizations, users, and API keys
 - **SubGraph** (domain/aggregates.go): Tracks subgraph schemas with versioning