AudioButton now tries Piper TTS via /api/vocabulary/tts endpoint
first, falls back to Browser Web Speech API if unavailable.
Backend: New GET /api/vocabulary/tts?text=...&lang=de endpoint.
audio_service.py: Fixed presigned URL flow for MinIO download.
This gives the same high-quality voice as the Investor Agent
in the pitch deck (Thorsten DE / Lessac EN, MIT license).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
0f0bbc3dc0