Fix sidebar image sizing inconsistencies and improve overall image handling efficiency

[chubes4]

Problem

The sidebar component displays images without size constraints, showing full-height aspect ratios that break visual consistency with other sections of the site.

Current behavior:

• Sidebar images use WordPress 'medium_large' size (768px wide) with no CSS width/height restrictions
• Only visual styling applied: border-radius, overflow hidden, box-shadow
• Images display at natural aspect ratios within medium_large bounds

Affected files:

• extrachill/sidebar.php - Main sidebar template
• extrachill/inc/sidebar/recent-posts.php:93-95 - Image display logic
• extrachill/assets/css/sidebar.css:98-103 - CSS styling

Comparison with other sections:

• Archive/search images: Fixed 260px height with object-fit: cover
• Related posts: Fixed 160px height with object-fit: cover
• Single posts: Use 'large' size without constraints
• News wire/artist platform: Various sizes but inconsistent patterns

Proposed Solution

1. Add consistent width/height constraints to sidebar images (similar to archive/related posts)
2. Review and standardize image size usage across the entire theme
3. Optimize image loading efficiency (lazy loading, responsive images)
4. Ensure responsive behavior on mobile devices

Impact

• Improved visual consistency and user experience
• Better performance through optimized image sizes
• Mobile-responsive design improvements

Acceptance Criteria

• Sidebar images constrained to consistent dimensions
• No visual breaking changes to layout
• Images load efficiently across devices
• Consistent image handling patterns documented

Labels: enhancement, ux, performance, css