refactor(types): use CrawlerType as enum

[nipsysdev]

Pull Request: Refactor Crawler Type Implementation

Summary of Changes

This PR refactors the crawler type implementation to use a TypeScript enum (CrawlerType) instead of string literals. This change improves type safety and maintainability across the codebase.

Key Changes

1. Type Safety Enhancement

• Replaced string-based crawler types ("listing") with CrawlerType enum
• Updated import statements to include CrawlerType from core types

2. Configuration Structure Updates

• Simplified source configuration structure by removing the nested items object
• Moved container_selector and fields properties directly under listing

3. Core Type Definitions

• Updated core/types.ts to use the new CrawlerType enum
• Removed CRAWLER_TYPES constant in favor of the enum

4. Comprehensive Test Updates

• Updated all test files to use the new CrawlerType enum
• Modified test configurations to match the new structure
• Fixed optional chaining in content field assertions