graphs-v2026.08.tar.zst

Auto-fetch graph dataset via Docker Compose (graphs-init service)

Adds graphs-init and graph-archives-init one-shot services (built from
scripts/graphs-init.Dockerfile, a tiny Alpine image with bash/curl/tar/
zstd) that run scripts/get-graphs.sh / get-graph-archives.sh unmodified
before the app starts. server now depends_on graphs-init with condition:
service_completed_successfully, so plain 'docker compose up --build' is
enough on a fresh clone -- no separate script call required.

graph-archives-init is gated behind the 'archives' Compose profile since
it's a much larger, optional download; run with
'docker compose --profile archives up --build' or './start.sh --archives'.
Graph data still never enters the application image -- these are separate
one-shot containers, not a build step of server/Dockerfile.

start.sh simplified to a thin wrapper now that Compose handles fetching.
README updated to match.