Add scope and re-translation options to Apply Pre-Translation

The Crowdin API extends the **Apply Pre-Translation** (`api.projects.pre-translations.post`) request with re-translation controls in both Crowdin and Crowdin Enterprise. API client libraries should expose the new fields.

New fields:

- `scope` — which strings to apply pre-translation to: `untranslated` (default), `translated`, or `all`.
- `translationModifiedBefore` — re-translate only if the current translation was modified before this date (has effect when `scope` is `translated` or `all`).
- `replaceTranslationsOption` — whether to replace existing translations: `none` (default), `autoTranslated`, or `all`.
- `resetApprovalStatus` — remove approval on existing translations when applying pre-translations.

Deprecated:

- `translateUntranslatedOnly` is deprecated in favor of `scope` (`true` → `scope: untranslated`, `false` → `scope: all`) and cannot be combined with `scope` in the same request.

The fields carry mutual-exclusion constraints (e.g. `resetApprovalStatus` requires `scope` to be `translated`/`all` and cannot be combined with `skipApprovedTranslations` or `autoApproveOption`); see the API docs for the full rules.

**References:**
- [Apply Pre-Translation](https://support.crowdin.com/developer/api/v2/#operation/api.projects.pre-translations.post)
- Crowdin Enterprise: [Apply Pre-Translation](https://support.crowdin.com/developer/enterprise/api/v2/#operation/api.projects.pre-translations.post)

Start at the client entry point for the Crowdin API operation `api.projects.pre-translations.post` and inspect its request type and related tests. Compare the exposed fields, deprecation behavior, and mutual-exclusion rules with the linked Apply Pre-Translation API documentation; done means the new options and constraints are represented by the Go client.

Written by the indexing model from the issue text.