Add support for AI File Translation methods

The Crowdin API has been extended with new **AI File Translation** endpoints in the AI section, including operations to start translation, check translation status, cancel translation, download translated file, and download translated strings.

The Crowdin API client libraries should be updated to support these methods so developers can run and manage file-based AI translation workflows directly from SDKs.

**References:**
- [AI File Translations](https://support.crowdin.com/developer/api/v2/#tag/AI/operation/api.users.ai.file-translations.post)
- [Get File Translations Status](https://support.crowdin.com/developer/api/v2/#tag/AI/operation/api.users.ai.file-translations.get)
- [Cancel File Translations](https://support.crowdin.com/developer/api/v2/#tag/AI/operation/api.users.ai.file-translations.delete)
- [Download Translated File](https://support.crowdin.com/developer/api/v2/#tag/AI/operation/api.users.ai.file-translations.download)
- [Download Translated File Strings](https://support.crowdin.com/developer/api/v2/#tag/AI/operation/api.users.ai.file-translations.download-strings)

Start by reviewing the Go client's existing API methods for related AI operations and the Crowdin API references linked in the issue. Identify the appropriate client entry points and tests from those existing patterns. Done means the SDK supports starting, checking, cancelling, and downloading AI file translations and translated strings, with tests covering the methods.

Written by the indexing model from the issue text.