fix: mount FalkorDB volume to correct data path

[Tunde-cs]

Summary

Fix incorrect Docker volume mount path in mcp_server/docker/docker-compose-falkordb.yml.
The volume was mounted to /data (a symlink into the container's writable layer) instead
of /var/lib/falkordb/data (where FalkorDB actually writes dump.rdb). Data appeared to
persist across restarts but was silently lost on docker compose down, --force-recreate,
or image rebuilds.

Type of Change

• Bug fix

Objective

N/A

Testing

• Unit tests added/updated
• Integration tests added/updated
• All existing tests pass

Verified on a running stack:

• docker exec docker-falkordb-1 ls /var/lib/falkordb/data/ → dump.rdb present
• docker run --rm -v docker_falkordb_data:/check alpine ls /check/ → dump.rdb in the named volume

make check passes (format, lint, pyright, unit tests).

Breaking Changes

• This PR contains breaking changes

Checklist

• Code follows project style guidelines (make lint passes)
• Self-review completed
• Documentation updated where necessary
• No secrets or sensitive information committed