App 2.39.1, server 2.8.0: map roads from OpenFreeMap, on demand

The public Overpass answered 429/502 and needs ~40 s a tile while the
car gives up after 8 s, so the server cancelled its queries and the
car's retries added load. Now the server fetches only the tiles a car
asks for, as OpenStreetMap vector tiles from OpenFreeMap (MAP_TILES_URL),
decodes the transportation layer with a small reader of its own, and
keeps each tile 30 days on a volume (MAP_CACHE_DIR). A fetch finishes
even after the car has stopped waiting; the car hears 503 with
Retry-After and gets the tile on its next try.

App: OpenFreeMap/OpenMapTiles attribution on the map, retry after 15 s.

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

AGENTS.md

@@ -21,7 +21,7 @@ MG4 head unit (Android 9, AAOS, MT2712)
 - **server/** — Go 1.27 API at `https://car.k8s.stinnesbeck.com`: stores telemetry, consumption
   and charging in InfluxDB, pairs cars by QR code, carries settings typed on a phone, relays
   app releases from the private forge, and serves the roads for the Grid's map from
-  OpenStreetMap (Overpass). It does **not** talk to ABRP. See `server/README.md`.
+  OpenStreetMap vector tiles (OpenFreeMap), fetched per tile on demand and cached on a volume. It does **not** talk to ABRP. See `server/README.md`.
 - **k8s/** — plain Kubernetes manifests (InfluxDB, server, Grafana with three provisioned
   dashboards, Traefik routes). See `k8s/README.md`.
 - **EVHardware/** — vendored shared vehicle layer (PolyForm Noncommercial, see `LICENSE.md`).