docs(blog): add HappyHorse 1.1 video model article

[alabulei1]

Summary

• Add a ByteFuture Writings article introducing HappyHorse-1.1 on Token Station
• Cover native synchronized audio, T2V/I2V model IDs, 720P/1080P pricing, and usage examples
• Add the article to posts.json

Validation

• Static article checks passed: three-column layout, Recent/Topics sidebar, TOC script, Token Station CTA, no stale tokens.bytefuture.ai CTA, no old campaign carryover
• Local browser preview verified at http://127.0.0.1:8765/blog/happyhorse-1-1-native-audio-video-generation-token-station.html
• Mobile CSS sanity checked: viewport meta, pre overflow, grid min-width, sidebars hidden at <=1024px

Notes

• This PR intentionally ships the English article only and removes i18n redirect/selector from this page so it does not link to missing translated article pages. Translations can follow in a separate PR.