feat: router.back() navigation, read-only evaluation view, auth audit logging

- Convert all Back buttons platform-wide (38 files) to use router.back()
  for natural browser-back behavior regardless of entry point
- Add read-only view for submitted evaluations in closed rounds with
  blue banner, disabled inputs, and contextual back navigation
- Add auth audit logs: MAGIC_LINK_SENT, PASSWORD_RESET_LINK_CLICKED,
  PASSWORD_RESET_LINK_EXPIRED, PASSWORD_RESET_LINK_INVALID
- Learning Hub links navigate in same window for all roles
- Update settings descriptions to reflect all-user scope

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/layouts/role-nav.tsx

@@ -142,8 +142,6 @@ export function RoleNav({ navigation, roleName, user, basePath, statusBadge, edi
                   <a
                     key={item.name}
                     href={item.href}
-                    target="_blank"
-                    rel="noopener noreferrer"
                     className={className}
                     onClick={() => logNavClick.mutate({ url: item.href })}
                   >
@@ -291,8 +289,6 @@ export function RoleNav({ navigation, roleName, user, basePath, statusBadge, edi
                     <a
                       key={item.name}
                       href={item.href}
-                      target="_blank"
-                      rel="noopener noreferrer"
                       onClick={() => { logNavClick.mutate({ url: item.href }); setIsMobileMenuOpen(false) }}
                       className={className}
                     >