fix(neo4j): move data dirs from /data (S3 FUSE) to /tmp (local)

fix(neo4j): use /data for persistent storage, chown fallback to chmod 777

refactor(docker): switch to python:3.11-slim base, install neo4j via APT

fix(neo4j): bypass entrypoint, write neo4j.conf directly, start binary via supervisord

fix(neo4j): chown /data to neo4j in start.sh before supervisord starts neo4j

fix(neo4j): redirect data dirs to /tmp to avoid HF Spaces /data permission issue

feat: implement CC-RAG prototype with Neo4j, FastAPI, React