Add visual IconSelect grid for filter type picker in PP template editor

Replace plain filter type dropdown with icon grid showing each filter
with its icon and description. Selecting a filter immediately adds it
to the template (no separate "+" click needed).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/sw.js

@@ -7,7 +7,7 @@
  *   - Navigation: network-first with offline fallback
  */
 
-const CACHE_NAME = 'ledgrab-v19';
+const CACHE_NAME = 'ledgrab-v20';
 
 // Only pre-cache static assets (no auth required).
 // Do NOT pre-cache '/' — it requires API key auth and would cache an error page.