Task 12: BlogLayout.astro with BlogPosting JSON-LD and Article OG Meta Tags

Verification: npm run build — PASSED (64 pages built)

File: src/layouts/BlogLayout.astro

Features implemented:
1. Wraps BaseLayout, passing title, description, ogImage.
2. Injects BlogPosting JSON-LD schema via slot="head" with:
   - @type: BlogPosting
   - headline (from title prop)
   - author: Organization { name: "Randify" }
   - publisher: Organization { name: "Randify", logo: ImageObject }
   - datePublished (ISO 8601)
   - dateModified (ISO 8601, falls back to datePublished)
   - url (canonical)
   - description
   - inLanguage
3. OG type set to "article" via <meta property="og:type" content="article" /> in slot="head".
4. Article-specific meta tags added:
   - article:published_time
   - article:modified_time
5. Styled container: max-w-2xl mx-auto, matching GeneratorLayout spacing.
6. Header with title, accent dot, publication date, and conditional "Updated" label.
7. Prev/next post navigation with bilingual labels (EN/RU), arrow icons, and focus rings.
8. Named slot "related" for RelatedPosts component.

Props accepted:
- title: string
- description: string
- pubDate: Date | string
- modDate?: Date | string
- ogImage?: string
- lang?: Lang
- prevPost?: { slug: string; title: string }
- nextPost?: { slug: string; title: string }

Build output: 64 pages, 0 errors.