Staging operating hours and manual Kafka cleanup

The Atlas Infra staging environment now has scheduled start and stop automation managed through Terraform.

• start runs on weekdays at 08:00 in America/Fortaleza
• stop runs every day at 20:00 in America/Fortaleza
• Kafka cleanup remains available as a dedicated Lambda, but it is now invoked manually instead of through EventBridge

This change reduces the amount of always-on runtime in staging while keeping a manual recovery path for Kafka topic cleanup when operators actually need to reclaim space.

The Kafka cleanup Lambda:

• discovers topics by the prefixes declared in msk_cleanup_topic_name_prefixes
• deletes and recreates the matching topics
• keeps explicit topic definitions from msk_cleanup_topics available after cleanup

The cleanup flow is intentionally manual because Kafka topic deletion can take long enough that running it on a fixed schedule was not a good cost tradeoff.