Feat: implémentation front page Blog

- blog.json.php : réécriture — intro (writer), featured (pages field),
  articles triés par date desc (featured exclu de la liste)
- layout.css : .page-scrollable + .page-container (styles génériques
  pour pages scrollables type blog/article)
- Blog.svelte : page scrollable avec header intro, article featured
  (image large + excerpt), liste articles avec dividers, responsive
  mobile/tablet via @custom-media

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

site/templates/blog.json.php

@@ -1,23 +1,25 @@
 <?php
 
+$featured = $page->featured()->toPages()->first();
+
+$mapArticle = function($article) {
+  return [
+    'title' => $article->title()->value(),
+    'slug'  => $article->slug(),
+    'date'  => $article->date()->toDate('d/m/Y'),
+    'intro' => $article->intro()->excerpt(200),
+    'cover' => $article->cover()->toFile()?->url(),
+  ];
+};
+
+$articles = $page->children()->listed()->sortBy('date', 'desc');
+
 $specificData = [
-  'intro' => [
-    'title' => $page->introTitle()->value(),
-    'text' => $page->introText()->value()
-  ],
-  'articles' => $page->children()->listed()->sortBy('date', 'desc')->map(function($article) {
-    return [
-      'title' => $article->title()->value(),
-      'slug' => $article->slug(),
-      'url' => $article->url(),
-      'date' => $article->date()->toDate('Y-m-d'),
-      'dateFormatted' => $article->date()->toDate('d/m/Y'),
-      'intro' => $article->intro()->excerpt(200),
-      'cover' => $article->cover()->toFile()?->url(),
-      'authorName' => $article->authorName()->value(),
-      'authorPhoto' => $article->authorPhoto()->toFile()?->url()
-    ];
-  })->values()
+  'intro'    => $page->intro()->value(),
+  'featured' => $featured ? $mapArticle($featured) : null,
+  'articles' => ($featured ? $articles->not($featured) : $articles)
+    ->map($mapArticle)
+    ->values(),
 ];
 
 $pageData = array_merge($genericData, $specificData);