AI SEO 2026+ v4.0 full implementation

Implemented complete agentic layer: SSE events stream, AI search API, AI actions endpoint, atomic facts with confidence scores, FAQ for answer engines, contact endpoint with AI escalation, soft-404 fallback, OpenAPI 3.1 spec. Added 40+ AI meta tags, JSON-LD structured data (Person, WebSite, BreadcrumbList, SpeakableSpecification), cookie consent with GA4 integration.