Binary data (MP3 audio) was corrupted by resp.text(). Now detects
content-type and uses arrayBuffer() for audio/* and image/* responses.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
HTTPS pages cannot fetch from HTTP backend ports. Added Next.js
API route proxies for /api/vocabulary, /api/learning-units, /api/progress
that forward to backend-lehrer internally (same Docker network, HTTP).
All frontend pages now use same-origin requests (getApiBase = '')
instead of direct port:8001 connections.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>