Add value sources for dynamic brightness control on LED targets

Introduces a new Value Source entity that produces a scalar float (0.0-1.0)
for dynamic brightness modulation. Three subtypes: Static (constant),
Animated (sine/triangle/square/sawtooth waveform), and Audio-reactive
(RMS/peak/beat from mono audio source). Value sources can be optionally
attached to LED targets to control brightness each frame.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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

@@ -108,6 +108,12 @@ import {
     editAudioSource, deleteAudioSource, onAudioSourceTypeChange,
 } from './features/audio-sources.js';
 
+// Layer 5: value sources
+import {
+    showValueSourceModal, closeValueSourceModal, saveValueSource,
+    editValueSource, deleteValueSource, onValueSourceTypeChange,
+} from './features/value-sources.js';
+
 // Layer 5: calibration
 import {
     showCalibration, closeCalibrationModal, forceCloseCalibrationModal, saveCalibration,
@@ -317,6 +323,14 @@ Object.assign(window, {
     deleteAudioSource,
     onAudioSourceTypeChange,
 
+    // value sources
+    showValueSourceModal,
+    closeValueSourceModal,
+    saveValueSource,
+    editValueSource,
+    deleteValueSource,
+    onValueSourceTypeChange,
+
     // calibration
     showCalibration,
     closeCalibrationModal,