Improve shapefile rendering and GeoJSON export

[Tania526-sudo]

Currently, the shapefile is loaded and plotted, but not exported for GIS integration.

Suggested tasks:
- Read `.shp` file using `geopandas`
- Convert geometries to GeoJSON using `gdf.to_file("output.geojson", driver="GeoJSON")`
- Add CLI argument to choose export format

Useful libs: `geopandas`, `shapely`

Goal: ensure interoperability with external GIS tools like QGIS or Leaflet.js.