Add multilingual support (DE default, EN under /en/)

lib/Helper.php

@@ -1,8 +1,38 @@
 <?php
 
 class Helper {
-    public static function parseHolidays($config) {
-        $text = $config['holidays']['text'];
+    private static $currentLang = 'de';
+
+    public static function setLang($lang) {
+        self::$currentLang = ($lang === 'en') ? 'en' : 'de';
+    }
+
+    public static function getLang() {
+        return self::$currentLang;
+    }
+
+    /**
+     * Build a language-aware internal URL.
+     * German (default): / or /leistungen.html
+     * English: /en/ or /en/leistungen.html
+     */
+    public static function url($path = '/', $lang = null) {
+        $targetLang = $lang !== null ? $lang : self::$currentLang;
+        $cleanPath = '/' . ltrim($path, '/');
+        if ($cleanPath === '/index.php' || $cleanPath === '/main.html') {
+            $cleanPath = '/';
+        }
+        if ($targetLang === 'en') {
+            return $cleanPath === '/' ? '/en/' : '/en' . $cleanPath;
+        }
+        return $cleanPath;
+    }
+
+    public static function parseHolidays($config, $lang = null) {
+        $targetLang = $lang !== null ? $lang : self::$currentLang;
+        $text = ($targetLang === 'en' && !empty($config['holidays']['text_en']))
+            ? $config['holidays']['text_en']
+            : $config['holidays']['text'];
         $from = DateTime::createFromFormat('Y-m-d', $config['holidays']['from']);
         $until = DateTime::createFromFormat('Y-m-d', $config['holidays']['until']);
         $text = preg_replace('/\{\{from\}\}/', $from->format('d.m.Y'), $text);