feat(tts): integrate autonomous Piper neural TTS with zero-latency pre-warming for words and context

app/static/js/modules/ui.js

@@ -168,14 +168,34 @@ export function updateHeaderStats(total = 0, today = 0, srsCount = 0) {
 }
 
 // -----------------------------------------------------------------------
-// Audio Player Helper (Safe stub / audio stream)
+// Audio Player Helper (Safe stub / audio stream / Piper TTS)
 // -----------------------------------------------------------------------
-export function playAudio(url) {
-    if (!url) return;
+let activeAudio = null;
+
+export function playAudio(url, speed = 1.0) {
+    if (!url) return null;
     try {
+        if (activeAudio) {
+            try {
+                activeAudio.pause();
+                activeAudio.currentTime = 0;
+            } catch (e) {}
+        }
         const audio = new Audio(url);
+        if (speed && speed !== 1.0) {
+            audio.playbackRate = speed;
+        }
+        activeAudio = audio;
         audio.play().catch(e => console.warn('Audio playback not supported or blocked:', e));
+        return audio;
     } catch (e) {
         console.warn('Audio play error:', e);
+        return null;
     }
 }
+
+export function playTextSpeech(text, lang = 'en', speed = 1.0) {
+    if (!text || !text.trim()) return null;
+    const url = `/api/tts?text=${encodeURIComponent(text.trim())}&lang=${lang}&speed=${speed}`;
+    return playAudio(url, speed);
+}