feat(templates): add archive-header and post-grid components

- Add ArchiveHeader component (schema, renderer, formbuilder)
- Add PostGrid component (schema, renderer, formbuilder)
- Unify archive templates (home, archive, category, tag,
  author, date, search)
- Add page visibility system with VisibilityDefaults
- Register components in AdminDashboardRenderer
- Fix boolean conversion in functions-addon.php
- All 172 unit tests passed

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Admin/Shared/Infrastructure/FieldMapping/FieldMapperProvider.php

@@ -33,6 +33,8 @@ final class FieldMapperProvider
         'Footer',
         'ThemeSettings',
         'AdsensePlacement',
+        'ArchiveHeader',
+        'PostGrid',
     ];
 
     public function __construct(