feat: enhance person scraper with employment type extraction and grouped experience parsing

[miguelcostero]

Summary

This PR enhances the PersonScraper with improved experience extraction capabilities:

• Employment Type Extraction: Added support for extracting employment type (Full-time, Part-time, Contract, Freelance, etc.) from experience entries
• Grouped Experience Parsing: Improved parsing of grouped/nested experiences where multiple roles are listed under a single company
• Better Fallback Logic: Details page is now tried first, with main page as fallback for more reliable data extraction

Changes

Models

• Added employment_type field to the Experience model

Person Scraper

• Added EMPLOYMENT_TYPE_MAP for normalizing employment type values
• New methods for parsing grouped experiences:
  • _get_experiences_from_details() - Extract from details/experience page
  • _get_experiences_from_main_page() - Fallback extraction from main profile
  • _parse_grouped_main_page_role() - Parse nested roles on main page
  • _parse_grouped_details_experience() - Parse grouped entries from details page
  • _parse_grouped_detail_role() - Parse individual role in grouped experience
• Helper methods:
  • _is_experience_time_text() - Detect date/duration text
  • _normalize_employment_type() - Normalize employment type strings
  • _extract_employment_type_from_text() - Extract employment type from text
  • _split_company_and_employment_type() - Split company name from employment type

Tests

• Added HTML fixtures for grouped experiences (main page and details page)
• Added unit tests for grouped experience parsing