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/accounts/$accountId/enrollments.tsx

@@ -20,7 +20,7 @@ function statusBadge(status: string) {
 }
 
 const columns: Column<Enrollment & { memberName?: string }>[] = [
-  { key: 'member_name', header: 'Member', sortable: true, render: (e) => <span className="font-medium">{(e as any).memberName ?? e.memberId}</span> },
+  { key: 'member_name', header: 'Member', sortable: true, render: (e) => <span className="font-medium">{e.memberName ?? e.memberId}</span> },
   { key: 'status', header: 'Status', sortable: true, render: (e) => statusBadge(e.status) },
   { key: 'start_date', header: 'Start', sortable: true, render: (e) => <>{new Date(e.startDate + 'T00:00:00').toLocaleDateString()}</> },
   { key: 'rate', header: 'Rate', render: (e) => <>{e.rate ? `$${e.rate}${e.billingInterval ? ` / ${e.billingInterval} ${e.billingUnit}` : ''}` : <span className="text-muted-foreground">—</span>}</> },
@@ -41,7 +41,7 @@ function AccountEnrollmentsTab() {
       <div className="flex items-center justify-between">
         <p className="text-sm text-muted-foreground">{data?.pagination.total ?? 0} enrollment(s)</p>
         {hasPermission('lessons.edit') && (
-          <Button size="sm" onClick={() => navigate({ to: '/lessons/enrollments/new', search: {} as any })}>
+          <Button size="sm" onClick={() => navigate({ to: '/lessons/enrollments/new', search: {} as Record<string, unknown> })}>
             <Plus className="h-4 w-4 mr-1" />Enroll a Member
           </Button>
         )}
@@ -55,7 +55,7 @@ function AccountEnrollmentsTab() {
         total={data?.data?.length ?? 0}
         onPageChange={() => {}}
         onSort={() => {}}
-        onRowClick={(e) => navigate({ to: '/lessons/enrollments/$enrollmentId', params: { enrollmentId: e.id }, search: {} as any })}
+        onRowClick={(e) => navigate({ to: '/lessons/enrollments/$enrollmentId', params: { enrollmentId: e.id }, search: {} as Record<string, unknown> })}
       />
     </div>
   )