Cache: fix 1-year CSS cache and add version busting

- .htaccess: remove duplicate cache block that set all CSS/JS to max-age=31536000
  CSS/JS now use max-age=3600 must-revalidate (was 1 year, breaking live edits)
- index.php: bump main.min.css version v1.1.3 -> v1.1.4
- All 78 PHP files: add ?v=20260222 to main.css and cro-enhancements.css refs
  Forces browser cache bust for all pages after todays accessibility changes

blog/articles/ecommerce-trends-uk-2025.php

@@ -49,7 +49,7 @@ $breadcrumbs = [
     
     <link rel="canonical" href="https://ukdataservices.co.uk/blog/articles/<?php echo $article_slug; ?>">
     
-    <link rel="stylesheet" href="/assets/css/main.css">
+    <link rel="stylesheet" href="/assets/css/main.css?v=20260222">
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
     <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap" rel="stylesheet">