feat: YouTube music download system with admin dashboard

Sidecar architecture: edge functions (auth + DB) → youtube-worker container
(youtubei.js for playlist metadata, yt-dlp for audio downloads).

- Edge functions: youtube-playlist, youtube-process, youtube-status (CRUD)
- youtube-worker sidecar: Node.js + yt-dlp, downloads M4A to Supabase Storage
- Admin music page: import playlists, process queue, inline genre editing
- 12 music genres with per-track assignment and import-time defaults
- DB migrations: download_jobs, download_items tables with genre column
- Deploy script and CI workflow for edge functions + sidecar

youtube-worker/Dockerfile

@@ -0,0 +1,21 @@
+FROM node:20-slim
+
+# Install yt-dlp (standalone binary) and ffmpeg for audio extraction
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends python3 ffmpeg curl ca-certificates && \
+    curl -L https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp -o /usr/local/bin/yt-dlp && \
+    chmod +x /usr/local/bin/yt-dlp && \
+    apt-get remove -y curl && \
+    apt-get autoremove -y && \
+    rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY package.json package-lock.json* ./
+RUN npm install --production
+
+COPY server.js ./
+
+EXPOSE 3001
+
+CMD ["node", "server.js"]