Remove VOLUME instruction from Dockerfile

VOLUME ["/data"] was causing Docker to create an anonymous volume for
/data that shadowed the bind mount defined in docker-compose.yml,
leaving the container with an empty /data instead of the host data.
The bind mount in docker-compose.yml is sufficient; no Dockerfile
VOLUME needed.

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

Dockerfile

@@ -13,6 +13,5 @@ COPY server.js ./
 COPY --from=build /app/build ./build
 
 ENV DATA_DIR=/data
-VOLUME ["/data"]
 EXPOSE 4000
 CMD ["node", "server.js"]