Copenhagen Phase 1: scaffolding + area + OSM download

- pyproject.toml with all deps (geopandas, contextily, partridge, etc.)
- config/: area.json (3 OSM boundary relations), modes.yaml (subway/s_tog/
  light_rail/regional/bus, S-tog scoped to route=light_rail network=Takst),
  styling.yaml (zorder/widths/colours/palette/mask/labels)
- build_area.py: fetch 3 relations via OSM API, stitch rings, dissolve to
  area.gpkg/area.geojson (City Pass approximation)
- download_osm.py: per-mode Overpass (mirror+backoff, out geom + recurse for
  stops), writes {mode}.gpkg (lines+stops) + query text
- download_gtfs.py / gtfs_to_geopackage.py: stubs (blocked on Rejseplanen)
- data/ gitignored (regenerable); output/ tracked

copenhagen/config/area.json

@@ -0,0 +1,9 @@
+{
+  "description": "City Pass area approximation: Copenhagen Kommune + Frederiksberg Kommune + Amager island (dissolved).",
+  "source": "OpenStreetMap API relation/{id}/full.json",
+  "relations": [
+    {"name": "Kobenhavns Kommune", "id": 2192363},
+    {"name": "Frederiksberg Kommune", "id": 2186660},
+    {"name": "Amager", "id": 5175924}
+  ]
+}