- Implement POST /api/keywords/enhance for AI keyword expansion
- Add keyword suggestion and validation endpoints
- Support SEO optimization with long-tail keyword generation
- Include rate limiting and comprehensive keyword validation
- Add related keyword discovery and categorization
- Mock AI integration ready for OpenAI GPT-4 connection
Resolves requirement §76 for keyword enhancement API.
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Co-Authored-By: Claude <noreply@anthropic.com>