Gettext backend for phoenix_kit_ai.

Owns the translation catalogues under priv/gettext/. Locale is set per-request by the parent application; this module is only responsible for looking msgids up against the active locale.

See guides/per-module-i18n.md in phoenix_kit core for the full setup and conventions — a relative guides/ path doesn't resolve for a Hex consumer, since that directory isn't shipped in core's package files:.