CARTO's free anonymous dark_all tiles (basemaps.cartocdn.com) now return a
200 OK "API KEY REQUIRED" watermark image for every tile instead of an
actual map or an error, so the map silently broke without any network or
API failure to notice -- the backend and /api/places were always healthy.
Confirmed by rendering the live page, not just curling the API.
Swapped to Esri's World_Dark_Gray_Base, a long-standing free, keyless
public basemap with a similar dark aesthetic. Native tiles stop at zoom
16; maxNativeZoom lets Leaflet upscale past that instead of requesting
invalid deeper tiles when zoomed in on a cluster.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>