feat: BindableFloat — universal value source binding for all scalar properties

Introduce BindableFloat abstraction that allows any numeric property to be
either a static value or dynamically driven by a ValueSource. Backward-compatible
serialization: plain float when unbound, {value, source_id} dict when bound.

Backend:
- storage/bindable.py — BindableFloat dataclass + bfloat() helper
- 25+ scalar properties converted across all entity types
- Runtime VS acquisition in ColorStripStreamManager for CSS bindings
- All stream hot loops use self.resolve() for live values
- KeyColorsColorStripStream now inherits ColorStripStream

Frontend:
- BindableScalarWidget (slider + VS picker toggle) for all editors
- TypeScript BindableFloat type + helpers
- Graph editor edges for all bindable properties
- Audio source channel IconSelect grid

Fixes: daylight longitude, candlelight wind_strength/candle_type from_dict

server/src/wled_controller/static/js/features/audio-sources.ts

@@ -30,6 +30,8 @@ class AudioSourceModal extends Modal {
 
     onForceClose() {
         if (_audioSourceTagsInput) { _audioSourceTagsInput.destroy(); _audioSourceTagsInput = null; }
+        if (_asChannelIconSelect) { _asChannelIconSelect.destroy(); _asChannelIconSelect = null; }
+        if (_asBandIconSelect) { _asBandIconSelect.destroy(); _asBandIconSelect = null; }
     }
 
     snapshotValues() {
@@ -58,6 +60,7 @@ let _asDeviceEntitySelect: EntitySelect | null = null;
 let _asParentEntitySelect: EntitySelect | null = null;
 let _asBandParentEntitySelect: EntitySelect | null = null;
 let _asBandIconSelect: IconSelect | null = null;
+let _asChannelIconSelect: IconSelect | null = null;
 
 const _svg = (d: string): string => `<svg class="icon" viewBox="0 0 24 24">${d}</svg>`;
 
@@ -136,7 +139,7 @@ export async function showAudioSourceModal(sourceType: any, editData?: any) {
         } else if (editData.source_type === 'mono') {
             _loadMultichannelSources(editData.audio_source_id);
             (document.getElementById('audio-source-channel') as HTMLSelectElement).value = editData.channel || 'mono';
-            (document.getElementById('audio-source-channel') as HTMLSelectElement).onchange = () => _autoGenerateAudioSourceName();
+            _ensureChannelIconSelect();
         } else if (editData.source_type === 'band_extract') {
             _loadBandParentSources(editData.audio_source_id);
             (document.getElementById('audio-source-band') as HTMLSelectElement).value = editData.band || 'bass';
@@ -155,7 +158,7 @@ export async function showAudioSourceModal(sourceType: any, editData?: any) {
             await _loadAudioDevices();
         } else if (sourceType === 'mono') {
             _loadMultichannelSources();
-            (document.getElementById('audio-source-channel') as HTMLSelectElement).onchange = () => _autoGenerateAudioSourceName();
+            _ensureChannelIconSelect();
         } else if (sourceType === 'band_extract') {
             _loadBandParentSources();
             (document.getElementById('audio-source-band') as HTMLSelectElement).value = 'bass';
@@ -426,6 +429,28 @@ function _ensureBandIconSelect() {
     });
 }
 
+const _icon = (d: string) => `<svg class="icon" viewBox="0 0 24 24">${d}</svg>`;
+
+function _ensureChannelIconSelect() {
+    const sel = document.getElementById('audio-source-channel') as HTMLSelectElement | null;
+    if (!sel) return;
+    const items = [
+        { value: 'mono',  icon: _icon(P.headphones), label: t('audio_source.channel.mono'),  desc: t('audio_source.channel.mono.desc') },
+        { value: 'left',  icon: _icon(P.volume2),    label: t('audio_source.channel.left'),  desc: t('audio_source.channel.left.desc') },
+        { value: 'right', icon: _icon(P.volume2),    label: t('audio_source.channel.right'), desc: t('audio_source.channel.right.desc') },
+    ];
+    if (_asChannelIconSelect) {
+        _asChannelIconSelect.updateItems(items);
+        return;
+    }
+    _asChannelIconSelect = new IconSelect({
+        target: sel,
+        items,
+        columns: 3,
+        onChange: () => _autoGenerateAudioSourceName(),
+    });
+}
+
 function _loadBandParentSources(selectedId?: any) {
     const select = document.getElementById('audio-source-band-parent') as HTMLSelectElement | null;
     if (!select) return;