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/data_sources.yaml

@@ -0,0 +1,35 @@
+# Data Sources Configuration
+# All external data source URLs should be configured here
+
+arcgis:
+  cable_url: "https://services.arcgis.com/6DIQcwlPy8knb6sg/ArcGIS/rest/services/SubmarineCables/FeatureServer/2/query"
+  landing_point_url: "https://services.arcgis.com/6DIQcwlPy8knb6sg/ArcGIS/rest/services/SubmarineCables/FeatureServer/1/query"
+  cable_landing_relation_url: "https://services.arcgis.com/6DIQcwlPy8knb6sg/ArcGIS/rest/services/SubmarineCables/FeatureServer/3/query"
+
+fao:
+  landing_point_url: "https://data.apps.fao.org/catalog/dataset/1b75ff21-92f2-4b96-9b7b-98e8aa65ad5d/resource/b6071077-d1d4-4e97-aa00-42e902847c87/download/landing-point-geo.csv"
+
+telegeography:
+  cable_url: "https://raw.githubusercontent.com/lintaojlu/submarine_cable_information/main/cable.json"
+  landing_point_url: "https://raw.githubusercontent.com/lintaojlu/submarine_cable_information/main/landing_point.json"
+
+huggingface:
+  models_url: "https://huggingface.co/api/models"
+  datasets_url: "https://huggingface.co/api/datasets"
+  spaces_url: "https://huggingface.co/api/spaces"
+
+cloudflare:
+  radar_device_url: "https://api.cloudflare.com/client/v4/radar/http/summary/device_type"
+  radar_traffic_url: "https://api.cloudflare.com/client/v4/radar/http/timeseries/requests"
+  radar_top_locations_url: "https://api.cloudflare.com/client/v4/radar/http/top/locations"
+
+peeringdb:
+  ixp_url: "https://www.peeringdb.com/api/ix"
+  network_url: "https://www.peeringdb.com/api/net"
+  facility_url: "https://www.peeringdb.com/api/fac"
+
+top500:
+  url: "https://top500.org/lists/top500/list/2025/11/"
+
+epoch_ai:
+  gpu_clusters_url: "https://epoch.ai/data/gpu-clusters"