TestsPage 'Updated' column: compute lastActivityDate() from the most
recent available timestamp — blue_validated_at > red_validated_at >
blue_work_started_at > blue_started_at > red_started_at > created_at.
Also fixes the sort-by-updated_at case.
ValidatedTestsPage 'Validated' column: use blue_validated_at (when Blue
Lead approved) falling back to red_validated_at. Fixes both the display
and the default sort-by-validated.
- New /tests/validated page with its own route and sidebar link, showing
only validated tests with Attack and Detection result badges.
- Removed the duplicate "My Pending Tasks" sidebar entry (same as All Tests).
- All Tests table no longer shows validated tests; clicking the Validated
counter card navigates to the new page instead.
- Validated option removed from the state filter dropdown in All Tests.
kitos