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

admin-web/components/sidebar.tsx

@@ -10,6 +10,7 @@ import {
   Users,
   FolderOpen,
   ImageIcon,
+  Music,
   LogOut,
   Flame,
 } from "lucide-react";
@@ -20,6 +21,7 @@ const navItems = [
   { href: "/trainers", label: "Trainers", icon: Users },
   { href: "/collections", label: "Collections", icon: FolderOpen },
   { href: "/media", label: "Media", icon: ImageIcon },
+  { href: "/music", label: "Music", icon: Music },
 ];
 
 export function Sidebar() {