fix: SpessaSynth init retry + default SF3 auto-load

- getAudioContext() calls SonicSF.init on every call (not just first)
- soundfontPlayer.init retries after 1s if SpessaSynth module not loaded yet
- Auto-loads sgm_v2.01 SF3 on successful init
- Fixes race condition: module script loads after regular scripts

app/static/js/services/soundfontPlayer.js

@@ -41,15 +41,25 @@
 
         // ── SpessaSynth init ──
         init: async function (audioContext) {
-            if (_initialized) return;
+            if (_initialized && _synthInstance) return;
             if (!window.SpessaSynthClass) {
-                console.warn("[SonicSF] SpessaSynth not loaded. Using oscillator fallback.");
+                console.warn("[SonicSF] SpessaSynth not loaded yet. Retrying in 1s...");
+                // Retry once after module script loads
+                setTimeout(() => {
+                    if (!_initialized && window.SpessaSynthClass && audioContext) {
+                        this.init(audioContext);
+                    }
+                }, 1000);
                 return;
             }
             try {
                 _synthInstance = new window.SpessaSynthClass(audioContext.destination);
                 _initialized = true;
                 console.log("[SonicSF] SpessaSynth initialized.");
+                // Auto-load default SF3
+                if (_currentSfId === null) {
+                    this.loadSoundFont("sgm_v2.01");
+                }
             } catch (e) {
                 console.error("[SonicSF] SpessaSynth init failed:", e);
             }