audio_service.py: Connects to compliance-tts-service (Piper TTS,
MIT license) for high-quality German (Thorsten) and English (Lessac)
voices. Audio cached as MP3 on first request.
vocabulary_api.py: New endpoints:
- GET /vocabulary/word/{id}/audio/{lang} — word pronunciation
- GET /vocabulary/word/{id}/audio-syllables/{lang} — slow syllable-by-syllable
Anton App analysis: identified 5 features to adopt (star system,
games as rewards, progress bars, listening exercises, matching exercises).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
