Add per-language Crowdin translation sync

[ZacharyZcR]

Overview

Adds a manual, per-language translation synchronization workflow for dev branches.

Changes

• Upload reviewed repository translations for one selected Crowdin language
• Machine-translate only untranslated strings in that language
• Download only the selected language to avoid changing unrelated locales
• Validate downloaded JSON and commit changes back to the dev branch
• Allow the existing pre-translation script to target selected language IDs while preserving its current all-language release behavior

Validation

• Workflow YAML parsed successfully
• Node syntax check passed
• git diff --check passed

[ZacharyZcR]

Closing this in favor of the project's existing Crowdin-first translation workflow. Translation changes will be made directly through Crowdin and synchronized during release.