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/css/streams.css

@@ -459,9 +459,6 @@ body.pp-filter-dragging .pp-filter-drag-handle {
 }
 
 .pp-add-filter-row {
-    display: flex;
-    gap: 8px;
-    align-items: center;
     margin-bottom: 4px;
 }