Cost controls: AI spend caps + storage tiering dashboards

[AKogut]

Context

Give operators visibility and guardrails over the two cost drivers: AI tokens and storage.

Scope

• Per-project/tenant AI spend caps with alerts
• Storage usage + tiering (hot executions vs cold rollups vs artifacts)
• Operator dashboard for cost drivers
• Enforcement hooks (throttle RCA / shorten retention when over budget)

Acceptance criteria

• An operator can see and cap AI + storage spend per tenant