feat(content): add NEM wallet v2.7.2 news article

[ymuichiro]

Closes #106. Added the complete localized news article set for the Issue-provided English manuscript.

• Issue-provided body: en 417, preserved without omissions; only control markers were removed and the external image source was migrated to the local asset.
• Auto-translated locales: ko 418, zh 419, zh-Hant-TW 420, ja 421. All retain the same image, six release bullets, and release link.
• Localizations are complete across all five files.
• Local validation passed: npm --prefix static-site run build and npm --prefix static-site run test, including link and sitemap checks.
• Generated top pages link both each new article and an existing article: /news/417, /ko/news/418, /zh/news/419, /zh-hant-tw/news/420, /ja/news/421. Public top-page verification remains after merge/deployment.