feat: TTS-Settings je Sprache, Audio-Coverage entkoppelt, Veröffentlichen-Workflow

- tts_settings (voice/model/speed/... pro Sprache) + Seed de/en/sv; Route /api/tts-settings
- audios: Stimme/Parameter aus tts_settings; Coverage zählt jetzt auch draft/translated
- pairs: GET /publishability (Readiness, sortierbar nach 'am wenigsten fehlt'),
  POST /:id/publish (kaskadiert question/statements→published, validiert Bild+Audio je Sprache)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/index.js

@@ -41,6 +41,7 @@ app.use('/api/user-names', auth, require('./routes/user-names'));
 app.use('/api/users-public', auth, require('./routes/users-public'));
 app.use('/api/users', auth, require('./routes/users'));
 app.use('/api/audios', auth, require('./routes/audios'));
+app.use('/api/tts-settings', auth, require('./routes/tts-settings'));
 app.use('/api/claude', auth, require('./routes/claude'));
 
 // 404