✅ Export Data as CSV
-----------------------------------
use Illuminate\Support\Facades\DB;

public function exportSubscribers()
{
    header('Content-Type: text/csv');
    header('Content-Disposition: attachment; filename=subscribers_'.date('Y-m-d_H-i-s').'.csv');
    
    $output = fopen('php://output', 'w');
    fputcsv($output, ['SL', 'Email']);
    
    $subscribers = DB::table('subscribers')
                   ->where('status', 1)
                   ->orderBy('id', 'ASC')
                   ->get();
    
    $i = 0;
    foreach ($subscribers as $row) {
        $i++;
        fputcsv($output, [$i, $row->email]);
    }
    
    fclose($output);
    exit;
}