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/heart-full-of-gratitude.md

@@ -54,25 +54,3 @@ AIA isn't just a workplace, it's a growing community built on love, patience, an
 Thank you, Rula Diab
 
 ![clinical director rula diab signature](/assets/images/clinical-director-rula-diab.png)
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-###### [Why Emotional Regulation Should Be the Heart of Every ABA Program](emotional-regulation-aba)
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-###### [Why My Child Can Talk but Still Struggles Socially](social-pragmatic-communication-autism)
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