feat: add Russian language translation

[aglitchman]

This PR adds Russian (ru) translation for the admin dashboard.

What

• Translated strings for all UI components in ru.json.
• Validated the file using the yarn i18n:validate ru.json: ru.json matches the schema.

Why

To make the admin panel more accessible and user-friendly for Russian-speaking users.

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Latest commit: fd45e80

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