refactor(admin): Migrate AdminAjaxHandler to Clean Architecture

- Move AdminAjaxHandler to Admin/Shared/Infrastructure/Api/Wordpress/
- Create FieldMapperInterface for decentralized field mapping
- Create FieldMapperRegistry for module discovery
- Create FieldMapperProvider for auto-registration of 12 mappers
- Add FieldMappers for all components:
  - ContactFormFieldMapper (46 fields)
  - CtaBoxSidebarFieldMapper (32 fields)
  - CtaLetsTalkFieldMapper
  - CtaPostFieldMapper
  - FeaturedImageFieldMapper (15 fields)
  - FooterFieldMapper (31 fields)
  - HeroFieldMapper
  - NavbarFieldMapper
  - RelatedPostFieldMapper (34 fields)
  - SocialShareFieldMapper
  - TableOfContentsFieldMapper
  - TopNotificationBarFieldMapper (17 fields)
- Update functions.php bootstrap with FieldMapperProvider
- AdminAjaxHandler reduced from ~700 to 145 lines
- Follows SRP, OCP, DIP principles

BACKUP BEFORE: Removing CTA A/B Testing legacy system

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

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

Admin/Hero/Infrastructure/FieldMapping/HeroFieldMapper.php

@@ -0,0 +1,65 @@
+<?php
+declare(strict_types=1);
+
+namespace ROITheme\Admin\Hero\Infrastructure\FieldMapping;
+
+use ROITheme\Admin\Shared\Domain\Contracts\FieldMapperInterface;
+
+/**
+ * Field Mapper para Hero Section
+ *
+ * RESPONSABILIDAD:
+ * - Mapear field IDs del formulario a atributos de BD
+ * - Solo conoce sus propios campos (modularidad)
+ */
+final class HeroFieldMapper implements FieldMapperInterface
+{
+    public function getComponentName(): string
+    {
+        return 'hero';
+    }
+
+    public function getFieldMapping(): array
+    {
+        return [
+            // Visibility
+            'heroEnabled' => ['group' => 'visibility', 'attribute' => 'is_enabled'],
+            'heroShowOnDesktop' => ['group' => 'visibility', 'attribute' => 'show_on_desktop'],
+            'heroShowOnMobile' => ['group' => 'visibility', 'attribute' => 'show_on_mobile'],
+            'heroShowOnPages' => ['group' => 'visibility', 'attribute' => 'show_on_pages'],
+
+            // Content
+            'heroShowCategories' => ['group' => 'content', 'attribute' => 'show_categories'],
+            'heroShowBadgeIcon' => ['group' => 'content', 'attribute' => 'show_badge_icon'],
+            'heroBadgeIconClass' => ['group' => 'content', 'attribute' => 'badge_icon_class'],
+            'heroTitleTag' => ['group' => 'content', 'attribute' => 'title_tag'],
+
+            // Colors
+            'heroGradientStart' => ['group' => 'colors', 'attribute' => 'gradient_start'],
+            'heroGradientEnd' => ['group' => 'colors', 'attribute' => 'gradient_end'],
+            'heroTitleColor' => ['group' => 'colors', 'attribute' => 'title_color'],
+            'heroBadgeBgColor' => ['group' => 'colors', 'attribute' => 'badge_bg_color'],
+            'heroBadgeTextColor' => ['group' => 'colors', 'attribute' => 'badge_text_color'],
+            'heroBadgeIconColor' => ['group' => 'colors', 'attribute' => 'badge_icon_color'],
+            'heroBadgeHoverBg' => ['group' => 'colors', 'attribute' => 'badge_hover_bg'],
+
+            // Typography
+            'heroTitleFontSize' => ['group' => 'typography', 'attribute' => 'title_font_size'],
+            'heroTitleFontSizeMobile' => ['group' => 'typography', 'attribute' => 'title_font_size_mobile'],
+            'heroTitleFontWeight' => ['group' => 'typography', 'attribute' => 'title_font_weight'],
+            'heroTitleLineHeight' => ['group' => 'typography', 'attribute' => 'title_line_height'],
+            'heroBadgeFontSize' => ['group' => 'typography', 'attribute' => 'badge_font_size'],
+
+            // Spacing
+            'heroPaddingVertical' => ['group' => 'spacing', 'attribute' => 'padding_vertical'],
+            'heroMarginBottom' => ['group' => 'spacing', 'attribute' => 'margin_bottom'],
+            'heroBadgePadding' => ['group' => 'spacing', 'attribute' => 'badge_padding'],
+            'heroBadgeBorderRadius' => ['group' => 'spacing', 'attribute' => 'badge_border_radius'],
+
+            // Visual Effects
+            'heroBoxShadow' => ['group' => 'visual_effects', 'attribute' => 'box_shadow'],
+            'heroTitleTextShadow' => ['group' => 'visual_effects', 'attribute' => 'title_text_shadow'],
+            'heroBadgeBackdropBlur' => ['group' => 'visual_effects', 'attribute' => 'badge_backdrop_blur'],
+        ];
+    }
+}