W20 Product Update: Personal and Service API keys

API keys now come in two types: Personal and Service.

Personal keys behave like before — they inherit their owner's role and per-engine grants. Service keys carry their own role and per-engine scope, so a production worker isn't tied to any one teammate. A service key can be roleless and reach only the engines listed on it.

Also this week:

- Enable/disable engines. Switch an engine off to stop being billed for it; the configuration is preserved for when you switch it back on.
- Usage in every localization response. Each response now includes the model used, the LLM cost, and the localization token cost — useful if you're attributing translation cost back to an end user.

Full changelog: https://lingo.dev/changelog