fix: piano roll tab có thể play với soundfont

app/static/js/services/soundfontPlayer.js

@@ -2,20 +2,30 @@
 (function () {
     'use strict';
 
-    // Web Audio API fallback synth
-    let audioCtx = null;
-    let gainNode = null;
     const activeOscillators = {};
 
-    function getCtx() {
-        if (!audioCtx) {
-            audioCtx = new (window.AudioContext || window.webkitAudioContext)();
-            gainNode = audioCtx.createGain();
-            gainNode.gain.value = 0.3;
-            gainNode.connect(audioCtx.destination);
+    // Use the shared AudioContext from the main app (lazy init)
+    let __gainNode = null;
+    const getCtx = () => {
+        if (typeof getAudioContext === 'function') {
+            const ctx = getAudioContext();
+            if (!__gainNode) {
+                __gainNode = ctx.createGain();
+                __gainNode.gain.value = 0.3;
+                __gainNode.connect(ctx.destination);
+            }
+            return ctx;
         }
-        return audioCtx;
-    }
+        if (!window.__sharedAudioCtx) {
+            window.__sharedAudioCtx = new (window.AudioContext || window.webkitAudioContext)();
+        }
+        if (!__gainNode) {
+            __gainNode = window.__sharedAudioCtx.createGain();
+            __gainNode.gain.value = 0.3;
+            __gainNode.connect(window.__sharedAudioCtx.destination);
+        }
+        return window.__sharedAudioCtx;
+    };
 
     const SonicSF = {
         loadedFonts: {},
@@ -131,7 +141,7 @@
 
             osc.connect(noteGain);
             
-            const dest = destinationNode || gainNode || ctx.destination;
+            const dest = destinationNode || __gainNode || ctx.destination;
             noteGain.connect(dest);
 
             osc.start(startAt);