ragleap-graph v0.6.6

Adds Postgres-backed audit logging, fully opt-in via audit=AuditConfig(database_url=...). Records one event per call to upsert_document() and all 6 read methods. Graceful degradation matches the rest of the library - missing psycopg2, unreachable database, or a failed insert never blocks the real Neo4j operation. Requires the new 'audit' extra: pip install ragleap-graph[audit]. Live-verified against real Postgres and Neo4j together. Full suite: 87 passed, 1 skipped. Published to PyPI.