Add Russian localization

[iliamak]

Description

This PR adds Russian localization to File Converter.

Changes made

• Added Resources.ru.resx with Russian translations for UI elements
• Translated all main interface elements
• Translated error messages and system notifications
• Translated file type descriptions

Testing

• Translations have been proofread for accuracy and natural language flow
• Special characters are properly encoded
• All string resources from base file are covered

Related Issues

None

Additional Notes

The translation aims to maintain a balance between technical accuracy and natural Russian language usage. Some technical terms (like "preset") are transliterated rather than translated when that's the common practice in Russian software interfaces.