feat(blog): recreate article footer navigation and related posts

- add reusable live-site-faithful blog footer component
- extract previous, next, and related post data from article content
- remove duplicated footer fragments from multilingual articles
- document the repeatable footer extraction workflow

www/src/content/blog/en/autism-fall-break-routine-tips-halloween-thanksgiving.mdx

@@ -245,25 +245,3 @@ Ready to deepen your ABA toolkit? Schedule a [free consultation](../client-consu
   }
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-###### [Now Enrolling: AIA Preparatory Academy for Children Ages 2–6](aba-school-readiness-arizona)
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-###### [Why Emotional Regulation Should Be the Heart of Every ABA Program](emotional-regulation-aba)
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