Fresh `pnpm dev:services` checkouts came up with an empty
brouter_segments volume, so every routing request returned
"datafile not found" and the e2e suite's BRouter tests failed.
Add an entrypoint that runs download-segments.sh when /data/segments
has no rd5 files, then exec's the existing server command. Subsequent
starts find the populated volume and skip straight to the server.
Keep wget in the final image (previously stripped) so the entrypoint
can fetch segments at runtime.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
