feat: add data sources config system and Earth API integration

- Add data_sources.yaml for configurable data source URLs
- Add data_sources.py to load config with database override support
- Add arcgis_landing_points and arcgis_cable_landing_relation collectors
- Change visualization API to query arcgis_landing_points
- Add /api/v1/datasources/configs/all endpoint
- Update Earth to fetch from API instead of static files
- Fix scheduler collector ID mappings

backend/app/core/websocket/broadcaster.py

@@ -7,6 +7,7 @@ from typing import Dict, Any, Optional
 from app.core.websocket.manager import manager
 
 
+
 class DataBroadcaster:
     """Periodically broadcasts data to connected WebSocket clients"""