Add scraper initialization to the connectToMongoDB() startup flow:
- Import createScraperIndexes, initializeScheduler, and
registerSignalHandlers from their respective service modules
- Create scraper database indexes during MongoDB connection setup
- Conditionally start the cron scheduler when SCRAPER_ENABLED is true
- Register SIGTERM/SIGINT signal handlers for graceful shutdown
All scraper initialization is wrapped in try/catch so failures are
logged but do not prevent the server from starting. This ensures
existing API functionality remains unaffected even if scraper
components encounter errors during startup.
Add 11 integration tests covering startup behavior, error resilience,
SCRAPER_ENABLED guard, and signal handler registration.
