refactor: make blog feature and content improvements

[f15u]

Type

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

These are bugs fixed:

• Featured post no longer duplicated in both hero and grid
• Prev/Next orientation was inverted (newest-first list, but Previous pointed to the newer post)
• Trailing slashes on RSS links / share links, conflicting with trailingSlash: "never"
• Author names weren't XML-escaped in the RSS feed
• Dates formatted in build-host timezone instead of UTC (off-by-one-day risk)
• Client hydration mismatch on /blog?category=x (category read from window during the render instead of after)
• Two client islands serializing overlapping post data → collapsed into one (BlogIndex)
• getCollection was called once per static page (171×) instead of once
• Dead readingTime schema field removed; "release" → "releases" typo in suggested tags fixed

Related

• Related Issue #
• Closes #