Fix progress message and auto-fetch GTFS-RT data

[chtitux]

Fixed two issues:

1. Corrected progress message during ZIP loading phase

   • Changed from "Extracting GTFS ZIP file" to "Loading and extracting GTFS ZIP file"
   • More accurate since this phase includes both downloading (if URL) and extraction
   • Located in gtfs-sqljs.ts:207

2. Auto-fetch GTFS-RT data when feed URLs are configured

   • If realtimeFeedUrls are provided during initialization, RT data is now fetched automatically after GTFS static data is loaded
   • Happens after 100% progress is reported
   • Failures are logged as warnings but don't fail the entire load
   • Users no longer need to manually call fetchRealtimeData() initially
   • Subsequent updates can still be triggered manually with fetchRealtimeData()

Documentation updates:

• Updated README to indicate auto-fetch behavior
• Added note in Progress Phases section explaining RT fetch happens after 100%
• Clarified that RT data is ready to use immediately after fromZip() completes

This provides a better developer experience as RT data is available immediately without requiring a separate fetch call.