Add BRouter healthcheck so compose --wait blocks until routing is ready

Without a healthcheck, --wait considers BRouter healthy as soon as the
container starts, before it has loaded segments and opened its port.
The healthcheck probes the routing endpoint directly, matching the old
manual curl loop in CI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.dev.yml

@@ -23,6 +23,12 @@ services:
       - "17777:17777"
     volumes:
       - brouter_segments:/data/segments
+    healthcheck:
+      test: ["CMD-SHELL", "curl -sf 'http://localhost:17777/brouter?lonlats=13.4,52.5|13.5,52.5&profile=trekking&format=geojson' > /dev/null"]
+      interval: 10s
+      timeout: 10s
+      retries: 12
+      start_period: 30s
 
   prometheus:
     image: prom/prometheus:latest