A UK buyer can now create their own account at /portal/signup/. The screen
creates a Keycloak user through a least-privilege service account
(ixg-provisioning: manage-users, view-users) and the matching Django row as
a buyer, then sends them through the normal sign-in flow to the portal.
Staff status is derived from the role in the OIDC backend rather than
asserted, so a self-registered buyer is not staff and does not become staff
on a later sign-in. The platform root and the RBAC middleware now route
each role to its own portal, which also fixes a redirect loop that the
staff fix exposed for non-staff buyers.
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.
