Log mislukte logins als LOGIN_FAILED (fail2ban/rapportage), logger-threshold naar 5

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/Helpers/common_helper.php

@@ -329,3 +329,16 @@ if (!function_exists('get_password_requirements_nl')) {
         ];
     }
 }
+
+if (!function_exists('sanitize_log_user')) {
+    /**
+     * Make a username safe for use in a log line (prevents log injection):
+     * only [A-Za-z0-9_@.-+] is kept, everything else becomes "_", max 64 chars.
+     */
+    function sanitize_log_user(string $user): string
+    {
+        $user = substr(preg_replace('/[^A-Za-z0-9_@.\-+]/', '_', $user), 0, 64);
+
+        return $user === '' ? '-' : $user;
+    }
+}