fix(adsense): Anchor ocultos por defecto + más tamaños Vignette

Anchor Ads:
- Ocultos por defecto via CSS (opacity: 0, visibility: hidden)
- Solo se muestran cuando AdSense llena el slot (clase .ad-loaded)
- Ya no aparece espacio en blanco si no hay anuncio

Vignette Ads:
- Agregados tamaños: 728x90, 970x250, 970x90, 468x60, 320x100
- Nueva opción "auto" (recomendado) para formato automático
- Renderer actualizado para manejar todos los tamaños

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Admin/AdsensePlacement/Infrastructure/Ui/AdsensePlacementFormBuilder.php

@@ -639,10 +639,20 @@ final class AdsensePlacementFormBuilder
         // Tamano y opacidad
         $html .= '<div class="row g-2 mt-2">';
         $html .= '    <div class="col-6">';
-        $size = $this->renderer->getFieldValue($cid, 'vignette_ads', 'vignette_size', '300x250');
+        $size = $this->renderer->getFieldValue($cid, 'vignette_ads', 'vignette_size', 'auto');
         $html .= $this->buildSelect($cid . 'VignetteSize', 'Tamano',
             (string)$size,
-            ['300x250' => '300x250', '336x280' => '336x280', 'responsive' => 'Responsive']
+            [
+                'auto' => 'Auto (recomendado)',
+                '300x250' => '300x250 (Rectangle)',
+                '336x280' => '336x280 (Large Rectangle)',
+                '728x90' => '728x90 (Leaderboard)',
+                '970x250' => '970x250 (Billboard)',
+                '970x90' => '970x90 (Large Leaderboard)',
+                '468x60' => '468x60 (Banner)',
+                '320x100' => '320x100 (Large Mobile)',
+                'responsive' => 'Responsive (fluid)',
+            ]
         );
         $html .= '    </div>';
         $html .= '    <div class="col-6">';