The admin backfill lived only in Settings -> Advanced, so an admin staring at
the 'Uncategorised' row had no obvious way to fix it. Render the admin-only
RegionBackfillCard inline in the region section when uncategorised > 0, and
clarify the zero-state (remaining untagged pins belong to other mappers).
Spots created before reverse geocoding have coordinates but no city/country
tag, so the map draws them while /stats can only show "Uncategorised". Counted
on the canonical relay: 54 raw -> 43 after admin-hide -> 13 tagged / 30
uncategorised, and 21 of the 30 are the two admin accounts' own pins.
useRegionBackfill finds the logged-in user's own untagged spots/shops, decodes
each pin's coords (lat/lon else geohash), reverse-geocodes via the shared
reverseGeocodeRegions(), and republishes the addressable event with the region
tags added - preserving every existing tag. Publishes to getWriteRelays()
(community + author) so the canonical stats see it, spaced 1.1s for Nominatim's
1 req/s policy. Surfaced as an admin-only RegionBackfillCard in Settings ->
Advanced.
