Comprehensive Error Handling System

Major WebcrawlerAPI update: Comprehensive error handling system implementation

• Added two-level error handling system: job level and job item level errors
• New job level error codes:
  • insufficient_balance for balance-related issues
  • invalid_request for malformed requests
  • internal_error for system-level issues
• New job item level error codes:
  • host_returned_error for non-200 HTTP responses
  • website_access_denied for 403 responses
  • name_not_resolved for DNS resolution failures
  • internal_error for system-level issues
• Each error now includes detailed error messages and specific error codes for better debugging