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/dialogues/auth/RegisterDialog.vue

@@ -108,8 +108,19 @@ export default {
                 short = 'ceb';
             } else if (browserLanguage.startsWith('de')) {
                 short = 'de';
+            } else if (browserLanguage.startsWith('fr')) {
+                short = 'fr';
+            } else if (browserLanguage.startsWith('es')) {
+                short = 'es';
             } else {
-                short = 'en';
+                const prefs = navigator.languages || [browserLanguage];
+                if (prefs.some((l) => l.startsWith('fr'))) {
+                    short = 'fr';
+                } else if (prefs.some((l) => l.startsWith('es'))) {
+                    short = 'es';
+                } else {
+                    short = 'en';
+                }
             }
             const response = await apiClient.post('/api/settings/getparamvalueid', { paramValue: short });
             this.language = response.data.paramValueId;