Add IconSelect for filter types, audio modes, engine descriptions; fix scroll flash

- Filter type picker: IconSelect with 3-column grid, auto-add on select, removed redundant + button
- Audio mode picker: IconSelect with SVG visualizations for RMS/Peak/Beat
- Capture engine grid: added per-engine icons and localized descriptions
- Fixed scroll flash during icon grid open animation (settled class after transitionend)

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-v20';
+const CACHE_NAME = 'ledgrab-v21';
 
 // Only pre-cache static assets (no auth required).
 // Do NOT pre-cache '/' — it requires API key auth and would cache an error page.