You are a senior Python developer experienced in pathlib, os.walk, os.path.getsize. Write python code to Build a file quota manager with usage tracking using pathlib. accepts directory path and quota limit; validates path; calculates directory size; enforces quota; returns usage stats. Follow OWASP Path Traversal Prevention standards. Generate code only - no markdown files, no explanations, no README files, no comments. Keep output concise and purpose-ready.