fix: pass TICKETMASTER_API_KEY env var to backend container

Was missing from docker-compose environment list so the key was never
visible to the Node.js process even when set in .env.

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

docker-compose.yml

@@ -32,6 +32,7 @@ services:
       - MAX_PARALLEL=${MAX_PARALLEL:-2}
       - DOWNLOAD_BACKEND=${DOWNLOAD_BACKEND:-auto}
       - SQUID_QUALITY=${SQUID_QUALITY:-mp3}
+      - TICKETMASTER_API_KEY=${TICKETMASTER_API_KEY}
     command: >
       sh -c "
         apt-get update && apt-get install -y --no-install-recommends python3 python3-pip ffmpeg curl git && rm -rf /var/lib/apt/lists/* &&