Task 21: RelatedPosts Component
================================

Files created:
- src/components/RelatedPosts.astro

Files modified:
- src/i18n/translations.ts (added relatedPosts key: en="Related posts", ru="Похожие статьи")
- src/pages/blog/[slug].astro (imported RelatedPosts, wired into "related" slot)
- src/pages/ru/blog/[slug].astro (imported RelatedPosts, wired into "related" slot)

Build result: PASS
- 83 pages built successfully
- No errors or warnings

Implementation details:
- Accepts post: CollectionEntry<"blog">
- Uses getCollection to fetch non-draft posts in same language
- Scores related posts by tag overlap count
- Shows top 3 posts with score > 0
- Hides section entirely if no related posts found
- Renders title, date, and description snippet for each related post
- Links use correct /blog/ or /ru/blog/ base path
- Styled with Tailwind matching existing dark theme (zinc palette, accent color)