The origin-zone map drew its background from a public tile server, which made it
the only part of the admin page that depended on a third-party domain — and the
part that breaks. Where a viewer's network, proxy or browser filter refuses
tile.openstreetmap.org (the refusal arrives as a 403) the map never draws, while
the page, the Leaflet bundle and the polygon data are all same-origin and fine.
Fetch the tiles server-side and serve them from /tiles/{z}/{x}/{y}.png: cached
on disk, so a page opened repeatedly does not re-fetch, and gated on being
signed in, so the route is not an open tile relay. The upstream stays
configurable via LEAFLET_TILE_URL, and LEAFLET_TILE_PROXY_ENABLED=False puts the
browser back on direct fetches.
When a tile still cannot be fetched, answer an empty tile rather than an error
page and say so under the map, instead of leaving a viewer with a blank grid and
no explanation.
ixgadmin
d5bc06802e