AI models and costs

/admin/ai-models shows estimated AI spend and editable pricing (JSON in platform_settings key ai_models).

Action	Permission
View pricing / costs	dashboard:read (all staff)
Edit pricing	settings:write (super_admin only)

Generations store cost_usd, prompt_tokens, completion_tokens, model_name, duration_ms, and client_ip. Costs are computed from token usage × rates (or per-call rates for image/audio providers).