added free text input with security measures

common.php

@@ -2,6 +2,8 @@
 // /var/www/html/common.php
 // Gemeinsame Helfer für Token-Validierung, Key-Derivation (HKDF) und AES (CBC, IV vorangestellt).
 
+require_once __DIR__ . '/lib/text_sanitize.php';
+
 /**
  * Load KEY=value pairs from .env in the project root.
  * Does not override variables already set in the real environment.