Completed documentation work for the current backlog items.
- Added testing and QA documentation in
docs/testing/index.md - Added performance tuning and optimization guidance in
docs/performance/index.md - Added security hardening and best practices documentation in
docs/security/index.md - Added observability and monitoring guidance in
docs/observability/index.md
These guides implement the requested scope and deliverables for the four open backlog issues.