Web player served by stemserve

Plex browsing, stem mixer with presets, shuffle, repeat all/one, playback
speed, queue, waveform seek. stemserve serves web/ at / without the token.
stemserve image now builds from the repo root.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/Dockerfile

@@ -1,8 +1,11 @@
+# Build from the repo root so the web player comes along:
+#   docker build -f server/Dockerfile -t stemserve .
 FROM python:3.12-alpine
 RUN apk add --no-cache ffmpeg
-COPY stemserve.py /app/stemserve.py
+COPY server/stemserve.py /app/server/stemserve.py
+COPY web /app/web
 ENV STEMS_DIR=/stems CACHE_DIR=/cache PORT=8765 PYTHONUNBUFFERED=1
 EXPOSE 8765
 # Unraid shares belong to nobody:users.
 USER 99:100
-CMD ["python", "/app/stemserve.py"]
+CMD ["python", "/app/server/stemserve.py"]