feat: Refactor database connection handling to use centralized configuration

inc/excelOperate.inc.php

@@ -1,5 +1,6 @@
 <?php
 require_once "vendor/autoload.php";
+include_once __DIR__."/config.php";
 use PhpOffice\PhpSpreadsheet\Reader\Csv;
 
 /**
@@ -26,7 +27,7 @@ function readMyExcel($file): array
  */
 function dbOp($data,$company)
 {
-    $mysqli = new mysqli('localhost', 'root', 'nancysimon', 'myquant');
+    $mysqli = get_mysqli_connection();
     $maxrow = count($data);
     $maxcol = count($data[0]);
     $msg = array();