Adds the central-side Audit Log page scaffold at /audit/log (M7-T1) and
introduces a new Audit nav group (M7-T9) that hosts both the new page and
the renamed Configuration Audit Log. The page body is intentionally a
heading + two placeholders — Bundle B will land the AuditFilterBar and
AuditResultsGrid behind them.
The Audit nav group sits between Monitoring and the per-user footer; both
items inside are Admin-only, so the section header lives inside the
RequireAdmin AuthorizeView (non-admins see no orphan header).
bUnit scaffold tests pin the page heading, the section header order, and
the two child links; the existing 338 CentralUI tests continue to pass.
