fix(content): restore omitted issue 103 paragraph

[ymuichiro]

Summary

• Restore the paragraph from Issue static-site/content/ja/newsに新しい記事を追加してください　2026年7月のブログ（日本語訳） #103 that was omitted from the July 2026 article.
• Add the corresponding translated paragraph to all five localized articles.
• Keep metadata, images, and unrelated content unchanged.

Root cause

PR #104 manually transferred the Issue body but skipped the paragraph between the Next steps heading and its bullet list. The build and deployment pipeline did not remove it; it was already absent from the Markdown source.

Validation

• npm --prefix static-site run build passed.
• npm --prefix static-site run test passed.
• Generated article pages contain the restored paragraph in all five locales.

Related to #103.