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/Query/PostGridQueryBuilder.php

@@ -0,0 +1,109 @@
+<?php
+declare(strict_types=1);
+
+namespace ROITheme\Shared\Infrastructure\Query;
+
+use ROITheme\Shared\Domain\Contracts\PostGridQueryBuilderInterface;
+
+/**
+ * Implementacion de PostGridQueryBuilderInterface
+ *
+ * RESPONSABILIDAD: Construir WP_Query a partir de parametros de filtro.
+ * No genera HTML ni obtiene settings.
+ *
+ * @package ROITheme\Shared\Infrastructure\Query
+ */
+final class PostGridQueryBuilder implements PostGridQueryBuilderInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function build(array $params): \WP_Query
+    {
+        $args = [
+            'post_type' => 'post',
+            'post_status' => 'publish',
+            'posts_per_page' => (int) ($params['posts_per_page'] ?? 9),
+            'orderby' => $params['orderby'] ?? 'date',
+            'order' => $params['order'] ?? 'DESC',
+            'paged' => (int) ($params['paged'] ?? 1),
+        ];
+
+        // Offset
+        if (!empty($params['offset'])) {
+            $args['offset'] = (int) $params['offset'];
+        }
+
+        // Filtro por categoria(s)
+        if (!empty($params['category'])) {
+            $args['category_name'] = $this->sanitizeSlugs($params['category']);
+        }
+
+        // Excluir categoria(s)
+        if (!empty($params['exclude_category'])) {
+            $excludeIds = $this->getCategoryIds($params['exclude_category']);
+            if (!empty($excludeIds)) {
+                $args['category__not_in'] = $excludeIds;
+            }
+        }
+
+        // Filtro por tag(s)
+        if (!empty($params['tag'])) {
+            $args['tag'] = $this->sanitizeSlugs($params['tag']);
+        }
+
+        // Filtro por autor
+        if (!empty($params['author'])) {
+            $author = $params['author'];
+            if (is_numeric($author)) {
+                $args['author'] = (int) $author;
+            } else {
+                $user = get_user_by('login', $author);
+                if ($user) {
+                    $args['author'] = $user->ID;
+                }
+            }
+        }
+
+        // Excluir posts por ID
+        if (!empty($params['exclude_posts'])) {
+            $excludeIds = array_map('intval', explode(',', $params['exclude_posts']));
+            $excludeIds = array_filter($excludeIds, fn($id) => $id > 0);
+            if (!empty($excludeIds)) {
+                $args['post__not_in'] = $excludeIds;
+            }
+        }
+
+        return new \WP_Query($args);
+    }
+
+    /**
+     * Sanitiza slugs separados por coma
+     */
+    private function sanitizeSlugs(string $slugs): string
+    {
+        $parts = explode(',', $slugs);
+        $sanitized = array_map('sanitize_title', $parts);
+        return implode(',', $sanitized);
+    }
+
+    /**
+     * Obtiene IDs de categorias desde slugs
+     *
+     * @return int[]
+     */
+    private function getCategoryIds(string $slugs): array
+    {
+        $parts = explode(',', $slugs);
+        $ids = [];
+
+        foreach ($parts as $slug) {
+            $term = get_term_by('slug', trim($slug), 'category');
+            if ($term instanceof \WP_Term) {
+                $ids[] = $term->term_id;
+            }
+        }
+
+        return $ids;
+    }
+}