generic API response + ICS: warehouse_balance md_rack update

app/assets/utils/db_auth.php

@@ -4,6 +4,11 @@ require_once __DIR__."/../../config.php";
 require_once __DIR__."/../../dbconn.php";
 require_once __DIR__."/db_helpers.php";
 
+// Tell the browser (and jQuery) the response body is JSON.
+// Without this, responses default to text/html, which prevents
+// xhr.responseJSON from being populated automatically in ajax_request().
+header('Content-Type: application/json; charset=utf-8'); 
+
 if(!empty($_SESSION["login_company_id"])){
 
     // CSRF Validation — add right at the top of the logged-in block