Use new Mosquito Alert observation feeds for Spain and Barcelona overlays

[Copilot]

Updated observation data sourcing to use the new lightweight Mosquito Alert CSV feeds (Spain: model_training_reports_lonlat.csv.gz, Barcelona: mosquito_alert_reports_used_in_model.csv) so maps can display the provided report points.

• Data loading
  • Added gzip-aware CSV loader fallback for .gz observation feeds.
• Configuration
  • Pointed Spain/Barcelona observation URLs to the new endpoints.
• Map overlays
  • Added observation point layer support (Leaflet/Mapbox), toggleable via “Observations,” with proper cleanup when switching regions or map types.

Example snippet:

// Load observations from configured feed and render as point layer
const observationsUrl = region.dataSources.mosquitoAlertES?.observationsUrl;
const csvData = await dataLoader.loadCSV(observationsUrl);
const features = csvData
  .filter(r => r.presence?.toString().toLowerCase() === 'true')
  .map(r => ({
    type: 'Feature',
    geometry: { type: 'Point', coordinates: [parseFloat(r.lon), parseFloat(r.lat)] }
  }));
mapManager.addObservationLayer({ type: 'FeatureCollection', features }, true, { color: '#ff7f00' });

• Screenshot: https://github.com/user-attachments/assets/48f81267-c223-463a-b5cc-2d66cb4840fd

Original prompt

Please revisit your pull request titled "Add mosquito-alert date-range aggregation and observation overlays #17". When I reviewed it I worried about problems with the large zipped data files you seemed to be trying to use, so I came up with a better solution: I now have the Spain and Barcelona pipelines outputting just the specific data that I want displayed on these maps. The locations are here:

Spain:
https://github.com/Mosquito-Alert/MosquitoAlertES/raw/refs/heads/main/data/model_training_reports_lonlat.csv.gz

Barcelona:
https://raw.githubusercontent.com/Mosquito-Alert/bcn/refs/heads/main/data/mosquito_alert_reports_used_in_model.csv

Please use these URLs to grab the data you need for displaying on both maps.

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