Optimize OpenUI Cloud media delivery and rendering

[zahlekhan]

Summary

• replace the generic client-heavy Cloud hero configuration with a dedicated server-rendered hero
• serve responsive 720 px and 1280 px WebP hero variants through native <picture> elements
• render one theme-aware image per feature instead of separate light and dark image nodes
• lazy-load below-the-fold feature media and provide responsive reports artwork
• losslessly optimize the retained SVG assets and replace oversized logo wrappers with compact WebPs
• add a main landmark, improve marketing contrast, and keep duplicate artwork decorative

Why

The Cloud page rendered both light and dark variants of large artwork and served oversized SVG/PNG assets. This increased transfer size, image scheduling, and LCP work even though only one visual variant was visible.

Impact

This is the media/rendering slice of #879. In the combined Lighthouse run, the page transfer size fell from 3.9 MB to 514 KiB and LCP fell from 18.6 s to 3.6 s. Those numbers are cumulative across the replacement PRs, not attributable to this PR alone.

Validation

• pnpm --dir docs types:check
• focused ESLint: 0 errors, one existing no-img-element warning in the animated logo strip
• desktop browser QA
• light/dark theme asset switching QA
• staged diff integrity check

Supersedes the Cloud media/rendering portion of #879.