feat: add Korean (ko-KR) translation

[moduvoice]

Motivation

This adds Korean (ko) translation support — to help Korean-speaking users use this
open-source project more comfortably in their own language.
(한국 사람들의 오픈소스 이용에 도움이 되게 하기 위해서 한글화 작업을 하였습니다.)

Changes

• Add locales/ko-KR.json with a full Korean translation of all CLI prompt text, mirroring the key structure of locales/en-US.json.
• No changes needed to utils/getLanguage.ts — it auto-discovers locale files by filename, so ko-KR.json is picked up automatically for systems with a ko_KR / ko-KR locale.

Testing

• Verified ko-KR.json has full key parity with en-US.json (same 38 leaf keys, same nesting, same order).
• Ran the existing __test__/locale.spec.ts suite (pnpm vp test __test__/locale.spec.ts) — all 5 locale-parity tests pass, including the new one for ko-KR.
• Ran vp fmt --check on the new file to confirm it matches the project's formatting conventions.