Implement PHP 8.5 release page redesign

[pronskiy]

This issue serves as a central place to coordinate the implementation of the redesign following the Design Contest winner.

@nunowar delivered the updated design implementation and processed several requested adjustments (hero height, compressed videos, code-block refinements). He can update content as needed but cannot handle the full integration into the PHP.net codebase.

To meet the November 20 release date, someone familiar with the current site infrastructure needs to integrate the design, merge in the latest content from #1454, and resolve remaining content issues.

Design repository: https://github.com/nunowar/phpnet
Preview: https://nunoguerra.com/dev/php/

Tasks

• Integrate design into php.net

• • Move HTML/CSS/JS from Nuno’s repo into releases/8.5/en.php
• • Adapt design to php.net templates (header/footer, includes, asset paths)
• • Ensure all assets load correctly within the existing infra
• • Open PR against the saundefined:php-85 branch

• Integrate final content

• Finalize design assets

• • Implement tabbed mobile layout for code examples
• • Add credits
    Footer should state:
    “Created as part of The PHP Foundation Design Contest.” with the link to PHP foundation post.

• Final validation

• • Desktop rendering check
• • Mobile check