feat: guided light meditation + Edge TTS neural voice audio

- Add continuous guided light-body-scan meditation (16 segments, 97% coverage)
- Edge TTS API endpoint with Xiaoxiao neural voice at -40% rate
- Pre-generated chime WAVs and guidance MP3s in public/audio/
- Mute toggle in practice page, sequenced non-overlapping audio
- Fix middleware to serve /audio and /api/audio/tts without auth
- All LLM output localized to Chinese; fix blank home/settings pages
- DeepSeek API compat: json_object, increased max_tokens
- Analytics, cron reminders, onboarding flow fixes

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/audio.ts

@@ -0,0 +1,50 @@
+// Audio playback using pre-generated files + server-side TTS API.
+// All functions silently no-op when audio playback fails.
+
+function playFile(path: string) {
+  try {
+    const audio = new Audio(path);
+    audio.play().catch(() => {});
+  } catch {}
+}
+
+export function playStartChime() {
+  playFile("/audio/start-chime.wav");
+}
+
+export function playTick() {
+  playFile("/audio/tick.wav");
+}
+
+export function playEndChime() {
+  playFile("/audio/end-chime.wav");
+}
+
+export function playMidGuidance(lang: string) {
+  const file = lang === "zh" ? "mid-guidance-zh.mp3" : "mid-guidance-en.mp3";
+  playFile(`/audio/${file}`);
+}
+
+export function playEndGuidance(lang: string) {
+  const file = lang === "zh" ? "end-guidance-zh.mp3" : "end-guidance-en.mp3";
+  playFile(`/audio/${file}`);
+}
+
+// Dynamic TTS via server-side Edge TTS (neural voices) API.
+// Falls back silently on error (network issue, edge-tts not installed, etc.).
+export async function speakText(text: string, lang: string = "zh"): Promise<void> {
+  try {
+    const url = `/api/audio/tts?text=${encodeURIComponent(text)}&lang=${lang}&rate=-40%25`;
+    const response = await fetch(url);
+    if (!response.ok) return;
+    const blob = await response.blob();
+    const blobUrl = URL.createObjectURL(blob);
+
+    await new Promise<void>((resolve) => {
+      const audio = new Audio(blobUrl);
+      audio.onended = () => { URL.revokeObjectURL(blobUrl); resolve(); };
+      audio.onerror = () => { URL.revokeObjectURL(blobUrl); resolve(); };
+      audio.play().catch(() => { URL.revokeObjectURL(blobUrl); resolve(); });
+    });
+  } catch {}
+}