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>

prisma/schema.prisma

@@ -57,6 +57,8 @@ model UserState {
   streakDays              Int      @default(0) @map("streak_days")
   totalSessionsCompleted  Int      @default(0) @map("total_sessions_completed")
   onboardingCompleted     Boolean  @default(false) @map("onboarding_completed")
+  onboardingVariant       String?  @map("onboarding_variant")
+  timezone                String   @default("Asia/Shanghai")
   lastSessionDate         DateTime? @map("last_session_date")
   updatedAt               DateTime @updatedAt @map("updated_at")
 
@@ -65,6 +67,18 @@ model UserState {
   @@map("user_states")
 }
 
+model AnalyticsEvent {
+  id        String   @id @default(uuid())
+  userId    String   @map("user_id")
+  event     String
+  metadata  String   @default("{}")
+  createdAt DateTime @default(now()) @map("created_at")
+
+  @@index([userId, createdAt])
+  @@index([event, createdAt])
+  @@map("analytics_events")
+}
+
 model Session {
   id              String    @id @default(uuid())
   userId          String    @map("user_id")