Add Defguard 1.6 release notes article with images and updated content

[piotr-bor]

Add Defguard 1.6 Release Notes Article

This PR adds the updated Defguard 1.6 release notes article with all images and improved content.

Changes

New Blog Article

• Article: defguard-1.6-release-notes.mdx - Complete release notes for Defguard 1.6
• Title: "Defguard 1.6 brings Zero-touch Enrollment at Enterprise Scale for WireGuard"
• Publish Date: 2025-12-19
• Hero Image: Release-1.6.png

Images Added

• Service Location configuration screenshot
• Traffic routing and Always-on VPN illustration
• macOS VPN integration screenshot
• External OpenID providers settings preview
• Full High Availability preview

Content Updates

• Updated title and description
• Expanded feature descriptions (Pre-logon, Always-on VPN, Zero-touch enrollment)
• Added details about Windows Client MSI and WireGuardNT
• Expanded Defguard 2.0 section with Components Orchestration and UI 2.0 details
• Improved ending section (removed awkward "Thank you")
• Added link to macOS migration guide

Files Changed

• src/content/blog/defguard-1.6-release-notes.mdx - New/updated article
• public/images/blog/defguard-1.6-release-notes/ - 6 images (hero + screenshots)

Testing

• ✅ Article displays correctly on blog listing page
• ✅ All images load properly
• ✅ Links are functional
• ✅ Content is properly formatted