Phase 10: Build settings management

[rpmoore]

Roadmap step 86 from docs/steps.md.

Scope

Build settings management.

Details

Manage DNS/admin listen addresses, cache TTL and size, block response mode, sinkhole settings, and query-log retention; show settings as active only after API confirmation.

References

• docs/steps.md Phase 10, step 86
• docs/plan/06-admin-api-ui.md#ui-screens
• docs/plan/05-persistence-config.md#configuration-reload
• docs/plan/03-policy-blocking.md#block-response-mode