fix: resolve all frontend lint errors and warnings

Replace all `any` types with proper types across 36 files:
- TanStack Router search params: `{} as Record<string, unknown>`
- API response pagination: proper typed interface
- DataTable column casts: remove unnecessary `as any`
- Function params and event handlers: use specific types
- Remove unused imports and variables in POS components

Frontend lint now passes with 0 errors and 0 warnings.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -81,8 +81,8 @@ function TemplatesListPage() {
   const columnsWithActions: Column<LessonPlanTemplate>[] = [
     ...columns,
     ...(canAdmin ? [{
-      key: 'actions' as any,
-      header: '' as any,
+      key: 'actions',
+      header: '',
       render: (t: LessonPlanTemplate) => (
         <Button variant="ghost" size="sm" onClick={(e) => { e.stopPropagation(); deleteMutation.mutate(t.id) }}>
           <Trash2 className="h-4 w-4 text-destructive" />
@@ -96,7 +96,7 @@ function TemplatesListPage() {
       <div className="flex items-center justify-between">
         <h1 className="text-2xl font-bold">Lesson Plan Templates</h1>
         {canAdmin && (
-          <Button onClick={() => navigate({ to: '/lessons/templates/new', search: {} as any })}>
+          <Button onClick={() => navigate({ to: '/lessons/templates/new', search: {} as Record<string, unknown> })}>
             <Plus className="mr-2 h-4 w-4" />New Template
           </Button>
         )}
@@ -126,7 +126,7 @@ function TemplatesListPage() {
         order={params.order}
         onPageChange={setPage}
         onSort={setSort}
-        onRowClick={(t) => navigate({ to: '/lessons/templates/$templateId', params: { templateId: t.id }, search: {} as any })}
+        onRowClick={(t) => navigate({ to: '/lessons/templates/$templateId', params: { templateId: t.id }, search: {} as Record<string, unknown> })}
       />
     </div>
   )