Fix: Clean output buffer in upload_profile_picture.php to prevent HTML in JSON response

- Move header() call to before any includes that might output
- Start output buffering at the beginning
- Clean output buffer before sending JSON response

src/processors/upload_profile_picture.php

@@ -1,14 +1,16 @@
 <?php
+ob_start(); // Start output buffering
 session_start();
+
+// Set JSON response header BEFORE any other output
+header('Content-Type: application/json');
+
 $rootPath = dirname(dirname(__DIR__));
 require_once($rootPath . "/src/config/env.php");
 require_once($rootPath . "/src/config/session.php");
 include_once($rootPath . '/src/config/connection.php');
 require_once($rootPath . "/src/config/functions.php");
 
-// Set JSON response header
-header('Content-Type: application/json');
-
 // Check database connection
 if (!isset($conn) || $conn === null) {
     die(json_encode(['status' => 'error', 'message' => 'Database connection failed']));
@@ -88,6 +90,8 @@ if (isset($_FILES['profile_picture']) && $_FILES['profile_picture']['error'] !=
     $response['message'] = 'No file uploaded or file error.';
 }
 
+// Clean output buffer and send only JSON
+ob_end_clean();
 echo json_encode($response);
 ?>