Bump service worker cache to v9 for CSS refresh

Force browsers to fetch the newly rebuilt CSS files with
all responsive utilities.

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

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

Author: etewiah

public/service-worker.js

@@ -1,9 +1,9 @@
 // PropertyWebBuilder Service Worker
 // Provides offline caching and performance optimization
 
-const CACHE_NAME = 'pwb-cache-v8';
-const STATIC_CACHE_NAME = 'pwb-static-v8';
-const IMAGE_CACHE_NAME = 'pwb-images-v8';
+const CACHE_NAME = 'pwb-cache-v9';
+const STATIC_CACHE_NAME = 'pwb-static-v9';
+const IMAGE_CACHE_NAME = 'pwb-images-v9';
 
 // Static assets to pre-cache
 const STATIC_ASSETS = [