Add Blog Post - Centralizing Outbound Traffic with AWS Private NAT Gateway

[aravind1801-p]

What is this article about?

R: A production-tested architecture for consolidating outbound traffic from multiple AWS runtime VPCs through a Private NAT Gateway, reducing partner firewall whitelisting from ~8,192 IPs or more to a single address via SNAT over a Site-to-Site VPN.

Checklist:

• I am added to the list of authors correctly.
  Aravind exists in content/authors/authors.json with avatar Aravind.png and role "System Engineer - Customer Success". The avatar file exists in content/authors/avatars/. The post metadata Authors: Aravind matches the key exactly.
• All images used in the post is in the correct folder (assets/images/post/).
  All 9 images referenced in the markdown exist in assets/: cover-image.png, centralizing-outbound-traffic.png, before-nat-gateway.png, architecture-overview.png, key-decisions.png, nat-vpc-design.png, packet-forward-return.png, successful-packet-delivery.png, operational-considerations.png.
• My article has been reviewed internally before opening this Pull Request.
  Internally reviewed in the recurring meetings.
• I have not modified someone else's previously published articles.
  The diff against main shows only the new post directory, author entry in authors.json, avatar, and package-lock.json. No existing posts were touched.
• I double checked my changes locally at http://127.0.0.1:4000/ after running bundle install && bundle exec jekyll serve.
  Verified locally at http://localhost:4200/. The post page, cover image, all content images, navigation, and homepage card all render correctly.
• My changes generate no new errors
  The dev server starts clean with no build errors.