feat: use spotdl (TzurSoffer fork) as primary Spotify resolver

Replaces rate-limited api.spotify.com calls with spotdl's SpotAPI
approach, which uses Spotify's internal browser endpoints — no
developer credentials needed, no api.spotify.com rate limits.
TOTP anonymous token kept as automatic fallback.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -34,7 +34,8 @@ services:
       - SPOTIFY_CLIENT_SECRET=${SPOTIFY_CLIENT_SECRET:-}
     command: >
       sh -c "
-        apk add --no-cache yt-dlp ffmpeg python3 &&
+        apk add --no-cache yt-dlp ffmpeg python3 py3-pip py3-requests git gcc musl-dev python3-dev libffi-dev &&
+        pip install --break-system-packages 'git+https://github.com/TzurSoffer/spotify-downloader' &&
         mkdir -p /deps && cd /deps && npm install express &&
         cd /app && NODE_PATH=/deps/node_modules node novasonic-server.js
       "