Fix #22: Medium-severity fixes (M-01 through M-07)

M-01: Host header injection - replaced HTTP_HOST with APP_DOMAIN
M-02: Unauthenticated CRUD - ownership checks on carDrivers add/delete
M-03: MD5 tracking token - replaced md5() with hash_hmac sha256
M-04: Webhook SMS - absolute log path instead of relative
M-05: Weak 3-digit OTP - already noted as requirement (Fix #5)
M-06: Redis without auth - added password + prefix to cancel_ride_by_driver
M-07: SSRF bypass - str_ends_with -> strict equality in allowlist

backend/ride/carDrivers/add.php

@@ -1,6 +1,12 @@
 <?php
 require_once __DIR__ . '/../../connect.php';
 
+// التحقق من أن المستخدم يملك هذا المعرف
+if ($role !== 'admin' && $role !== 'super_admin' && (string)$user_id !== (string)$driverID) {
+    jsonError("Unauthorized: You can only add cars to your own account");
+    exit;
+}
+
 // استقبال القيم
 $driverID          = filterRequest("driverID");
 $vin               = $encryptionHelper->encryptData(filterRequest("vin"));