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/js/features/streams.js

@@ -303,7 +303,7 @@ async function loadAvailableEngines() {
         // Update icon-grid selector with dynamic engine list
         const items = availableEngines
             .filter(e => e.available)
-            .map(e => ({ value: e.type, icon: getEngineIcon(e.type), label: e.name, desc: '' }));
+            .map(e => ({ value: e.type, icon: getEngineIcon(e.type), label: e.name, desc: t(`templates.engine.${e.type}.desc`) }));
         if (_engineIconSelect) { _engineIconSelect.updateItems(items); }
         else { _engineIconSelect = new IconSelect({ target: select, items, columns: 2 }); }
         _engineIconSelect.setValue(select.value);
@@ -2026,9 +2026,7 @@ const _FILTER_ICONS = {
 function _populateFilterSelect() {
     const select = document.getElementById('pp-add-filter-select');
     select.innerHTML = `<option value="">${t('filters.select_type')}</option>`;
-    const items = [
-        { value: '', icon: `<svg class="icon" viewBox="0 0 24 24">${P.wrench}</svg>`, label: t('filters.select_type') },
-    ];
+    const items = [];
     for (const f of _availableFilters) {
         const name = _getFilterName(f.filter_id);
         select.innerHTML += `<option value="${f.filter_id}">${name}</option>`;
@@ -2046,7 +2044,8 @@ function _populateFilterSelect() {
         _filterIconSelect = new IconSelect({
             target: select,
             items,
-            columns: 2,
+            columns: 3,
+            placeholder: t('filters.select_type'),
             onChange: () => addFilterFromSelect(),
         });
     }