Fix article links and include full content in PHP feeds

Two bugs found by testing real links from the feed:
- Link format was wrong (?news=<internal-id>), landing on the general
  listing instead of the article. Traced the real network call the site
  makes when opening an item and found the actual pattern:
  /actualites/<slug>?u=<UID> (agenda: /agenda/<slug>?u=<UID>), where the
  JS router reads the `u` query param to fetch @results?UID=...&fullobjects=1.
- Description only used the short teaser (description_fr) even though the
  API response already includes the full rich-text body (text_fr.data) and
  attachments (items[].file.download) in the same call — no extra request
  needed, just wasn't being used.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

php/actualites.php

@@ -30,13 +30,14 @@ function build_news_feed(): string
     $items = [];
     foreach (fetch_all_news() as $item) {
         $id = $item['id'] ?? '';
-        $summary = strip_html($item['description_fr'] ?? $item['description'] ?? null);
+        $title = $item['title_fr'] ?? $item['title'] ?? '(sans titre)';
+        $uid = $item['UID'] ?? $id;
         $items[] = [
-            'title' => $item['title_fr'] ?? $item['title'] ?? '(sans titre)',
-            'link' => SITE . '/actualites?news=' . rawurlencode($id),
-            'guid' => $item['UID'] ?? $id,
+            'title' => $title,
+            'link' => SITE . '/actualites/' . slugify($title) . '?u=' . rawurlencode($uid),
+            'guid' => $uid,
             'pubDate' => $item['effective'] ?? $item['created'] ?? null,
-            'description' => $summary,
+            'description' => full_body_html($item),
         ];
     }
     return build_rss(