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/index.html

@@ -173,8 +173,6 @@ placeholder="Enter address, intersection (e.g., Main St & Second St, City), or l
     </div>
 
     <script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js"></script>
-    <!-- Load shared theme utility -->
-    <script src="theme-utils.js"></script>
     <script src="utils.js"></script>
     <script src="app-mapbox.js"></script>