fix: replace invalid TanStack Router search casts with typed defaults

Newer TanStack Router enforces strict types on search params — 'search: {} as Record<string, unknown>' no longer satisfies routes with validateSearch. Replace all occurrences with the correct search shape for each destination route (pagination defaults for list routes, tab/field defaults for detail routes).

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

packages/admin/src/routes/_authenticated/lessons/plans/index.tsx

@@ -84,7 +84,7 @@ function LessonPlansPage() {
         order={params.order}
         onPageChange={setPage}
         onSort={setSort}
-        onRowClick={(p) => navigate({ to: '/lessons/plans/$planId', params: { planId: p.id }, search: {} as Record<string, unknown> })}
+        onRowClick={(p) => navigate({ to: '/lessons/plans/$planId', params: { planId: p.id }, search: { page: 1, limit: 25, q: undefined, sort: undefined, order: 'asc' as const } })}
       />
     </div>
   )