Switch basemap to ESRI WorldGrayCanvas (OSM tiles blocked)

OSM's tile server blocks apps without a valid identifying User-Agent
(contextily's default is a random UUID, which OSM rejects with an
'Access blocked' error tile). Switched to ESRI WorldGrayCanvas, a free
no-key light-gray basemap comparable to CartoDB Positron, and set a
proper User-Agent header (jetlag-maps/0.1) on contextily requests per
OSM tile usage policy.

copenhagen/scripts/render.py

@@ -28,7 +28,7 @@ from affine import Affine
 from adjustText import adjust_text
 from scipy.ndimage import distance_transform_edt
 
-from _common import CONFIG, OUTPUT, PROCESSED
+from _common import CONFIG, OUTPUT, PROCESSED, UA
 
 TARGET_CRS = "EPSG:3857"
 
@@ -97,7 +97,8 @@ def add_basemap(ax, styling, zoom=None):
         for part in provider.split("."):
             src = getattr(src, part)
         cx.add_basemap(ax, crs=TARGET_CRS, source=src, zoom=zoom,
-                       attribution=False, zorder=0)
+                       attribution=False, zorder=0,
+                       headers={"User-Agent": UA})
         return True
     except Exception as e:
         print(f"  [basemap] unavailable ({e}); using plain background", flush=True)