fix(jeu): overlay fonctionnel — CSS complet + URL sanitizée + data-state

- jeu.php : supprime les espaces de l'URL (preg_replace), ajoute data-state="initial" sur l'overlay
- Article.svelte : porte le CSS complet depuis l'ancienne app React
  (background opaque, play icon, hover, deactivate btn, game-active state)
- JS : ignore les clics sur overlay ended, remet data-state="initial" au deactivate

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

site/snippets/blocks/jeu.php

@@ -1,17 +1,19 @@
-<?php if ($block->url()->isNotEmpty()): ?>
+<?php if ($block->url()->isNotEmpty()):
+  $iframeUrl = preg_replace('/\s+/', '', $block->url()->value());
+?>
 <div class="iframe-game-container">
   <iframe
     loading="eager"
     importance="high"
     width="400"
     height="650"
-    style="border: none; overflow: hidden; pointer-events: none; display: block;"
-    src="<?= $block->url()->html() ?>"
+    style="border: none; overflow: hidden; pointer-events: none; display: block; width: 100%;"
+    src="<?= htmlspecialchars($iframeUrl, ENT_QUOTES, 'UTF-8') ?>"
   ></iframe>
-  <div class="iframe-click-overlay">
+  <div class="iframe-click-overlay" data-state="initial">
     <div class="overlay-content">
       <div class="play-icon">▶</div>
-      <p>Cliquez pour jouer</p>
+      <p class="overlay-message">Cliquez pour jouer</p>
     </div>
   </div>
   <button class="iframe-deactivate-btn" title="Deactivate game (restore scrolling)">✕</button>