docker: dedicated musician entrypoint + fuller runbook section

- docker/entrypoint.musician.sh: on a fresh /data volume, create the
  managed playlists and touch radio_log.log/persistence.log empty so the
  track-forwarding thread waits instead of crashing when Liquidsoap runs
  elsewhere; never overwrites preserved files
- Dockerfile.musician: wire the entrypoint, default CONJURER_MUSICIAN_BASE
  =/data (persist playlists/logs) and CONJURER_STREAM_TEMPLATE=/app/stream.html;
  declare the /data volume
- DOCKER_PROXMOX.md: expand the musician section (two volumes, preserving
  existing playlists, radio-log coupling, stream template)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docker/Dockerfile.musician

@@ -17,14 +17,19 @@ RUN pip install --no-cache-dir --upgrade pip \
     && pip install --no-cache-dir -r requirements_musician.txt
 
 COPY conjurer_musician/ ./
+COPY docker/entrypoint.musician.sh /usr/local/bin/entrypoint.sh
+RUN chmod +x /usr/local/bin/entrypoint.sh
 
 ENV PYTHONUNBUFFERED=1 \
     CONJURER_MUSICIAN_HOST=0.0.0.0 \
     CONJURER_MUSICIAN_PORT=5000 \
-    CONJURER_MUSIC_FOLDER=/music
+    CONJURER_MUSIC_FOLDER=/music \
+    CONJURER_MUSICIAN_BASE=/data \
+    CONJURER_STREAM_TEMPLATE=/app/stream.html
 
-# The mp3 library is mounted here (read-only is fine for serving).
-VOLUME ["/music"]
+# /music = the mp3 library (read-only ok); /data = writable playlists + logs.
+VOLUME ["/music", "/data"]
 EXPOSE 5000
 
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
 CMD ["python", "conjurer_musician.py"]

docker/entrypoint.musician.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+# Prepare the musician's writable volume so the web service starts cleanly on a
+# fresh container. Existing files are never overwritten (preserves your data).
+set -e
+
+DATA="${CONJURER_MUSICIAN_BASE:-/data}"
+MUSIC="${CONJURER_MUSIC_FOLDER:-/music}"
+mkdir -p "$DATA" "$DATA/logs" "$MUSIC"
+
+# The track-forwarding thread tails the Liquidsoap radio logs. When the radio
+# runs separately (or hasn't started yet) these files may not exist; create
+# them empty so the tailer waits instead of crashing.
+for f in radio_log.log persistence.log; do
+    [ -e "$DATA/$f" ] || : > "$DATA/$f"
+done
+
+# Ensure the managed playlists exist (routes/rescan also create them; this just
+# avoids a first-tick race before the initial scan).
+for f in all_playlist.playlist hit.playlist request.playlist priority_queue.playlist; do
+    [ -e "$DATA/$f" ] || : > "$DATA/$f"
+done
+
+exec "$@"