docs(readme): fix Kimi Code subscription link and price

The Kimi Code subscription link had drifted across the 5 README
translations: the English README pointed to https://www.kimi.com/kimiplus/sale
at $0.99, while the Japanese, Korean, Russian, and Simplified Chinese
versions pointed to https://www.kimi.com/membership/pricing with a
referral tracking ID, also at $0.99 with an "only this month" qualifier.

Normalized all 5 to the canonical https://www.kimi.com/code at $19,
preserving each language's localized "Kimi Code Subscription" wording.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.ko.md

@@ -135,7 +135,7 @@ Read this and tell me why it's not just another boilerplate: https://raw.githubu
 
 다음 구독만 있어도 ultrawork는 충분히 잘 돌아갑니다 (본 프로젝트와 무관하며, 개인적인 추천일 뿐입니다):
 - [ChatGPT 구독 ($20)](https://chatgpt.com/)
-- [Kimi Code 구독 ($0.99) (*이번 달 한정)](https://www.kimi.com/membership/pricing?track_id=5cdeca93-66f0-4d35-aabb-b6df8fcea328)
+- [Kimi Code 구독 ($19)](https://www.kimi.com/code)
 - [GLM Coding 요금제 ($10)](https://z.ai/subscribe)
 - 종량제(pay-per-token) 대상자라면 kimi와 gemini 모델을 써도 비용이 별로 안 나옵니다.