feat(i18n): add French language support and enhance localization

- Introduced French as a supported language across the application, updating locale files and adding translations for various components.
- Enhanced language handling logic to accommodate French, ensuring proper detection and fallback mechanisms.
- Updated UI elements to include French language options, improving accessibility for French-speaking users.
- Refactored SEO handling to include French in hreflang links, enhancing search engine indexing for multilingual content.
- Added new scripts for managing French translations and ensuring consistency across language files.

frontend/src/main.js

@@ -5,6 +5,7 @@ import router from './router';
 import './assets/styles.scss';
 import i18n from './i18n';
 import { setSeoI18nAccessor, applyRouteSeo } from './utils/seo';
+import { SUPPORTED_UI_LOCALES } from './i18n/supportedLocales.js';
 import { createVuetify } from 'vuetify';
 import * as components from 'vuetify/components';
 import * as directives from 'vuetify/directives';
@@ -25,7 +26,15 @@ function getBrowserLanguage() {
     if (browserLanguage.startsWith('de')) {
         return 'de';
     }
-    
+
+    if (browserLanguage.startsWith('fr')) {
+        return 'fr';
+    }
+
+    if (browserLanguage.startsWith('es')) {
+        return 'es';
+    }
+
     // Prüfe alle verfügbaren Sprachen für deutschsprachige Länder
     const allLanguages = navigator.languages || [navigator.language];
     for (const lang of allLanguages) {
@@ -47,13 +56,23 @@ function getBrowserLanguage() {
             }
         }
     }
-    
+
+    for (const lang of allLanguages) {
+        if (lang.startsWith('fr')) {
+            return 'fr';
+        }
+    }
+
+    for (const lang of allLanguages) {
+        if (lang.startsWith('es')) {
+            return 'es';
+        }
+    }
+
     // Fallback: Englisch für alle anderen Sprachen
     return 'en';
 }
 
-const SUPPORTED_UI_LOCALES = ['de', 'en', 'ceb', 'es'];
-
 function readLangFromUrl() {
     try {
         const q = new URLSearchParams(window.location.search).get('lang');