Fix language selector disappearing on navigation

- Remove missing theme-utils.js references from all HTML files
- Fix double initialization in i18n.js causing language selector conflicts
- Update service worker cache version to force fresh file loading
- Language selector now persists when navigating via snowflake icon

🤖 Generated with [Claude Code](https://claude.ai/code)

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

public/i18n.js

@@ -9,7 +9,6 @@ class I18nService {
     this.defaultLocale = 'en';
     this.availableLocales = ['en', 'es-MX'];
     this.currentLocale = this.getStoredLocale() || this.detectBrowserLocale();
-    this.loadTranslations();
   }
 
   /**