Phase 9: Fix & expand JSON-LD structured data

[elfensky]

Improve JSON-LD structured data across the site.

From the original issue:

• layout.jsx has {@type: WebSite}
• All individual page.jsx should have {@type: WebPage} with datePublished, dateModified, inLanguage, author
• All individual page.jsx should have {@type: BreadcrumbList}
• All events should get {@type: Event}

Current state: JSON-LD exists on layout and war page. Needs expansion to all pages.

Related: #123 (Phase 9 SEO & Meta)
Ref: docs/TODO.md Phase 9

[elfensky]

Merged into #123 — consolidated SEO issue.