App 2.39.0, server 2.7.0: Grid with map

A new Overview style: the Grid over the roads round the car from
OpenStreetMap, drawn in the floor's perspective, heading up, the bigger
roads glowing brighter, the car as a chevron.

Server: POST /v1/map/roads {z:14,x,y} fetches a tile's drivable roads
from Overpass (OVERPASS_URL; one request at a time, at least a second
apart), simplifies them to tile-local points in four classes, caches
them for 30 days and never logs the tile.

App: MapRoads keeps the 3x3 tiles round the car from its own cache or
the server; GPS only while the style is shown; bearing from the GPS or
from successive positions. Without GPS, server or roads the plain floor
says why. OSM attribution on screen and in LICENSE.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LhzAVaUyqcw5PkGjz4mWW6

LICENSE.md

@@ -18,6 +18,12 @@ Nils' MG4 is a fork of a chain of forks, all MIT:
 MIT requires the copyright notice to travel with any copy or substantial portion of the
 software. `LICENSE` names all of them; keep every line.
 
+## Map data
+
+The roads of the "Grid with map" style are © OpenStreetMap contributors, under the
+[Open Database Licence](https://opendatacommons.org/licenses/odbl/); the style shows that line
+whenever it draws them. The server fetches them from an Overpass API (`server/maps.go`).
+
 ## The EVHardware library
 
 `EVHardware/` (the shared vehicle layer from EVSuite) is source-available under the