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/TopNotificationBar/Infrastructure/FieldMapping/TopNotificationBarFieldMapper.php

@@ -0,0 +1,51 @@
+<?php
+declare(strict_types=1);
+
+namespace ROITheme\Admin\TopNotificationBar\Infrastructure\FieldMapping;
+
+use ROITheme\Admin\Shared\Domain\Contracts\FieldMapperInterface;
+
+/**
+ * Field Mapper para Top Notification Bar
+ *
+ * RESPONSABILIDAD:
+ * - Mapear field IDs del formulario a atributos de BD
+ * - Solo conoce sus propios campos (modularidad)
+ */
+final class TopNotificationBarFieldMapper implements FieldMapperInterface
+{
+    public function getComponentName(): string
+    {
+        return 'top-notification-bar';
+    }
+
+    public function getFieldMapping(): array
+    {
+        return [
+            // Visibility
+            'topBarEnabled' => ['group' => 'visibility', 'attribute' => 'is_enabled'],
+            'topBarShowOnMobile' => ['group' => 'visibility', 'attribute' => 'show_on_mobile'],
+            'topBarShowOnDesktop' => ['group' => 'visibility', 'attribute' => 'show_on_desktop'],
+            'topBarShowOnPages' => ['group' => 'visibility', 'attribute' => 'show_on_pages'],
+
+            // Content
+            'topBarIconClass' => ['group' => 'content', 'attribute' => 'icon_class'],
+            'topBarLabelText' => ['group' => 'content', 'attribute' => 'label_text'],
+            'topBarMessageText' => ['group' => 'content', 'attribute' => 'message_text'],
+            'topBarLinkText' => ['group' => 'content', 'attribute' => 'link_text'],
+            'topBarLinkUrl' => ['group' => 'content', 'attribute' => 'link_url'],
+
+            // Colors
+            'topBarBackgroundColor' => ['group' => 'colors', 'attribute' => 'background_color'],
+            'topBarTextColor' => ['group' => 'colors', 'attribute' => 'text_color'],
+            'topBarLabelColor' => ['group' => 'colors', 'attribute' => 'label_color'],
+            'topBarIconColor' => ['group' => 'colors', 'attribute' => 'icon_color'],
+            'topBarLinkColor' => ['group' => 'colors', 'attribute' => 'link_color'],
+            'topBarLinkHoverColor' => ['group' => 'colors', 'attribute' => 'link_hover_color'],
+
+            // Spacing
+            'topBarFontSize' => ['group' => 'spacing', 'attribute' => 'font_size'],
+            'topBarPadding' => ['group' => 'spacing', 'attribute' => 'padding'],
+        ];
+    }
+}