DBMason v0.1.0 - PostgreSQL control plane

Initial PostgreSQL control-plane release: encrypted saved connections, database and login-role lifecycle, allowlisted access presets, append-only audit events, native observability, guarded read-only data workspace, SQLite control plane, Docker deployment, and real PostgreSQL 17 plus Chromium validation. See README.md, SECURITY.md, docs/USER_GUIDE.md, and docs/VALIDATION_REPORT.md. Host CPU/RAM remains explicitly unavailable without an external metrics provider.