feat: Add Russian and Kazakh translations

[brian15274927-prog]

Summary

• Added Russian (ru) translations for all 38 localization keys
• Added Kazakh (kk) translations for all 38 localization keys

These translations cover calendar notifications, event invitations, RSVP responses, and date formats.

Languages Added

• Russian (ru) - Русский
• Kazakh (kk) - Қазақша

Test Plan

• Verified YAML syntax is valid
• All existing keys have ru and kk translations
• Date format templates follow locale conventions

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