fix(docker): resolve /app/data permission denied on volume mounts

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.

Dockerfile.goreleaser

@@ -21,6 +21,7 @@ RUN apk add --no-cache \
     ca-certificates \
     tzdata \
     curl \
+    su-exec \
     libpq \
     zstd-libs \
     lz4-libs \
@@ -47,11 +48,15 @@ COPY sub2api /app/sub2api
 # Create data directory
 RUN mkdir -p /app/data && chown -R sub2api:sub2api /app
 
-USER sub2api
+# Copy entrypoint script (fixes volume permissions then drops to sub2api)
+COPY deploy/docker-entrypoint.sh /app/docker-entrypoint.sh
+RUN chmod +x /app/docker-entrypoint.sh
 
 EXPOSE 8080
 
 HEALTHCHECK --interval=30s --timeout=10s --start-period=10s --retries=3 \
     CMD curl -f http://localhost:${SERVER_PORT:-8080}/health || exit 1
 
-ENTRYPOINT ["/app/sub2api"]
+# Run the application (entrypoint fixes /app/data ownership then execs as sub2api)
+ENTRYPOINT ["/app/docker-entrypoint.sh"]
+CMD ["/app/sub2api"]