Docker named volumes and host bind-mounts may be owned by root,
causing "open data/model_pricing.sha256: permission denied" when
the container runs as the non-root sub2api user.
Add an entrypoint script that fixes /app/data ownership before
dropping to sub2api via su-exec. Replace USER directive with the
entrypoint approach across all three Dockerfiles and update both
GoReleaser configs to include the script in Docker build contexts.
