docs: deprecate Heroku and DigitalOcean marketplace integrations

[sertugkaya]

Summary

• remove Heroku references from docs examples
• add a DigitalOcean deprecation warning to the existing Redis quickstart
• clean up stale Redis FAQ cloud-provider wording and regenerate llms-full.txt

Verification

• npm run check (from llms/)
• git diff --check HEAD~1..HEAD
• rg -n -i "heroku|Digital Ocean is planned|Initially we have|Upstash has native integration with" .
• curl -s -o /dev/null -w "%{http_code}\n" http://localhost:3333/redis/quickstarts/digitalocean
• curl -s -o /dev/null -w "%{http_code}\n" http://localhost:3333/redis/help/faq

[mintlify]

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Project	Status	Preview	Updated (UTC)
upstash	🟢 Ready	View Preview	May 12, 2026, 3:51 PM

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