Add review language setting

[Hanjo92]

Summary

• Add a registered gitRoast.reviewLanguage setting with Korean, English, and Japanese options.
• Surface the review language dropdown in the settings panel and refresh the voice summary after save.
• Pass the selected language into review requests, provider prompts, demo roasts, and CLI config.

Verification

• npm run check
• npm run package
• git diff --check

Closes #41