feat(theme): add [roi_post_grid] shortcode for static pages

- Create PostGridShortcodeRegistrar for WordPress shortcode registration
- Implement RenderPostGridUseCase following Clean Architecture
- Add PostGridQueryBuilder for custom WP_Query construction
- Add PostGridShortcodeRenderer for HTML/CSS generation
- Register shortcode in DIContainer with proper DI
- Add shortcode usage guide in post-grid admin panel
- Fix sidebar layout: add hide_for_logged_in check to wrapper visibility

Shortcode attributes: category, tag, author, posts_per_page, columns,
show_pagination, show_thumbnail, show_excerpt, show_meta, etc.

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

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

Shared/Infrastructure/Persistence/WordPress/WordPressComponentVisibilityRepository.php

@@ -61,15 +61,35 @@ final class WordPressComponentVisibilityRepository implements WrapperVisibilityC
     /**
      * {@inheritDoc}
      *
-     * Delega a PageVisibilityHelper que ya implementa:
+     * Evalúa múltiples criterios de exclusión:
+     * - hide_for_logged_in: Ocultar para usuarios logueados
      * - Visibilidad por tipo de página (home, posts, pages, archives, search)
      * - Exclusiones por categoría, post ID, URL pattern
      */
     public function isNotExcluded(string $componentName): bool
     {
+        // Verificar hide_for_logged_in
+        if ($this->shouldHideForLoggedIn($componentName)) {
+            return false;
+        }
+
         return PageVisibilityHelper::shouldShow($componentName);
     }
 
+    /**
+     * Verifica si debe ocultarse para usuarios logueados
+     */
+    private function shouldHideForLoggedIn(string $componentName): bool
+    {
+        $value = $this->getVisibilityAttribute($componentName, 'hide_for_logged_in');
+
+        if ($value === null) {
+            return false;
+        }
+
+        return $this->toBool($value) && is_user_logged_in();
+    }
+
     /**
      * Obtiene un atributo del grupo visibility desde la BD
      *