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/admin.html

@@ -188,7 +188,6 @@
     </footer>
 
     <!-- Load shared theme utility -->
-    <script src="theme-utils.js"></script>
     <script src="utils.js"></script>
     <script src="admin.js"></script>
 </body>