Replace the ScrapingMode enum with a proper strategy pattern implementation for content scraping.
This change introduces:
- New ContentScrapingStrategy abstract base class
- Concrete WebScrapingStrategy and LXMLWebScrapingStrategy implementations
- New Pydantic models for structured scraping results
- Updated documentation reflecting the new strategy-based approach
BREAKING CHANGE: ScrapingMode enum has been removed. Users should now use ContentScrapingStrategy implementations instead.
