feat: use IconSelect grid for frequency band selector in band extract editor

Replace plain HTML select with icon grid picker (bass/mid/treble/custom)
using volume, music, zap, and sliders icons for visual differentiation.

server/src/wled_controller/static/js/app.ts

@@ -148,7 +148,7 @@ import {
     showAudioSourceModal, closeAudioSourceModal, saveAudioSource,
     editAudioSource, cloneAudioSource, deleteAudioSource,
     testAudioSource, closeTestAudioSourceModal,
-    refreshAudioDevices, onBandPresetChange,
+    refreshAudioDevices,
 } from './features/audio-sources.ts';
 
 // Layer 5: value sources
@@ -474,7 +474,6 @@ Object.assign(window, {
     testAudioSource,
     closeTestAudioSourceModal,
     refreshAudioDevices,
-    onBandPresetChange,
 
     // value sources
     showValueSourceModal,