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/Di/DIContainer.php

@@ -42,6 +42,12 @@ use ROITheme\Shared\Domain\Contracts\WrapperVisibilityCheckerInterface;
 use ROITheme\Shared\Infrastructure\Persistence\WordPress\WordPressComponentVisibilityRepository;
 use ROITheme\Shared\Application\UseCases\CheckWrapperVisibilityUseCase;
 use ROITheme\Shared\Infrastructure\Wordpress\BodyClassHooksRegistrar;
+// Post Grid Shortcode (Plan post-grid-shortcode)
+use ROITheme\Shared\Domain\Contracts\PostGridQueryBuilderInterface;
+use ROITheme\Shared\Domain\Contracts\PostGridShortcodeRendererInterface;
+use ROITheme\Shared\Infrastructure\Query\PostGridQueryBuilder;
+use ROITheme\Shared\Infrastructure\Ui\PostGridShortcodeRenderer;
+use ROITheme\Shared\Application\UseCases\RenderPostGrid\RenderPostGridUseCase;
 
 /**
  * DIContainer - Contenedor de Inyección de Dependencias
@@ -493,4 +499,47 @@ final class DIContainer
         }
         return $this->instances['bodyClassHooksRegistrar'];
     }
+
+    // ===============================
+    // Post Grid Shortcode System
+    // ===============================
+
+    /**
+     * Obtiene el query builder para post grid shortcode
+     */
+    public function getPostGridQueryBuilder(): PostGridQueryBuilderInterface
+    {
+        if (!isset($this->instances['postGridQueryBuilder'])) {
+            $this->instances['postGridQueryBuilder'] = new PostGridQueryBuilder();
+        }
+        return $this->instances['postGridQueryBuilder'];
+    }
+
+    /**
+     * Obtiene el renderer para post grid shortcode
+     */
+    public function getPostGridShortcodeRenderer(): PostGridShortcodeRendererInterface
+    {
+        if (!isset($this->instances['postGridShortcodeRenderer'])) {
+            $this->instances['postGridShortcodeRenderer'] = new PostGridShortcodeRenderer(
+                $this->getCSSGeneratorService()
+            );
+        }
+        return $this->instances['postGridShortcodeRenderer'];
+    }
+
+    /**
+     * Obtiene el caso de uso para renderizar post grid shortcode
+     */
+    public function getRenderPostGridUseCase(): RenderPostGridUseCase
+    {
+        if (!isset($this->instances['renderPostGridUseCase'])) {
+            $this->instances['renderPostGridUseCase'] = new RenderPostGridUseCase(
+                $this->getPostGridQueryBuilder(),
+                $this->getPostGridShortcodeRenderer(),
+                $this->getComponentSettingsRepository()
+            );
+        }
+        return $this->instances['renderPostGridUseCase'];
+    }
 }