Show translation source language in TranslateBox

[adinhuric]

Summary

This PR implements a new feature that shows the detected language in the TranslateBox component of Telegram Desktop.

Implementation Details

• Uses Platform::Language::Recognize() to detect the language of the original message.
• Displays the detected language using LanguageName() in the TranslateBox UI.
• Fallbacks to "Unknown" if detection fails.
• Updates handled in translate_box.cpp.

Why this matters

The Android version of Telegram shows the source language for translations, but the Desktop version did not. This improves transparency and consistency across platforms.

Closes #28748

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