Add filesystem Library Scan (movies/tv/music) and a full Music library

- New admin Library Scan page walks the NAS mounts directly for movies,
  TV, and music not already in Radarr/Sonarr/local storage, and imports
  them with storage_type=scan (fully integrated: streamable, transcodable,
  listed in Admin) — Radarr/Sonarr import flows are untouched.
- New Music section (nav tab, album-grid browse, per-album track list,
  persistent bottom player with queue/seek) backed by a Track model and
  range-request audio streaming endpoint.
- MusicBrainz + Cover Art Archive integration (free, no API key) to fill
  in album art for scanned tracks, paced to their 1 req/sec rate limit.
- Mounted the NAS music share into CT104 (new mp2 LXC mountpoint,
  CIFS read-only) alongside the existing video mount.
- Optional Bluetooth/output-device picker on the player bar via the Audio
  Output Devices API (setSinkId) for already-paired speakers — Chrome/Edge
  only, since browsers can't pair new BT devices directly.

frontend/src/lib/musicPlayer.jsx

@@ -0,0 +1,92 @@
+import { createContext, useContext, useRef, useState, useCallback, useEffect } from "react";
+import { getTrackStreamUrl } from "./api";
+
+const MusicPlayerCtx = createContext(null);
+
+export const MusicPlayerProvider = ({ children }) => {
+  const audioRef = useRef(new Audio());
+  const [queue, setQueue] = useState([]);
+  const [index, setIndex] = useState(-1);
+  const [isPlaying, setIsPlaying] = useState(false);
+  const [progress, setProgress] = useState({ position: 0, duration: 0 });
+  const [outputDevices, setOutputDevices] = useState([]);
+  const [sinkId, setSinkId] = useState("default");
+  const sinkSupported = typeof audioRef.current.setSinkId === "function";
+
+  const current = index >= 0 ? queue[index] : null;
+
+  const refreshOutputDevices = useCallback(async () => {
+    if (!navigator.mediaDevices?.enumerateDevices) return;
+    try {
+      const devices = await navigator.mediaDevices.enumerateDevices();
+      const outs = devices.filter((d) => d.kind === "audiooutput");
+      setOutputDevices(outs.map((d, i) => ({ deviceId: d.deviceId, label: d.label || `Output ${i + 1}` })));
+    } catch { /* enumeration unsupported/denied — picker just won't populate */ }
+  }, []);
+
+  const selectOutput = useCallback(async (deviceId) => {
+    if (!sinkSupported) return;
+    try {
+      await audioRef.current.setSinkId(deviceId);
+      setSinkId(deviceId);
+    } catch { /* device may have disappeared (e.g. BT speaker turned off) — keep current output */ }
+  }, [sinkSupported]);
+
+  const playAt = useCallback((newQueue, startIndex) => {
+    setQueue(newQueue);
+    setIndex(startIndex);
+  }, []);
+
+  useEffect(() => {
+    const audio = audioRef.current;
+    if (!current) { audio.pause(); return; }
+    audio.src = getTrackStreamUrl(current);
+    audio.play().then(() => setIsPlaying(true)).catch(() => setIsPlaying(false));
+  }, [current]);
+
+  useEffect(() => {
+    const audio = audioRef.current;
+    const onTime = () => setProgress({ position: audio.currentTime, duration: audio.duration || 0 });
+    const onEnded = () => {
+      if (index >= 0 && index < queue.length - 1) setIndex(index + 1);
+      else setIsPlaying(false);
+    };
+    audio.addEventListener("timeupdate", onTime);
+    audio.addEventListener("ended", onEnded);
+    return () => {
+      audio.removeEventListener("timeupdate", onTime);
+      audio.removeEventListener("ended", onEnded);
+    };
+  }, [index, queue]);
+
+  const togglePlay = useCallback(() => {
+    const audio = audioRef.current;
+    if (!current) return;
+    if (audio.paused) audio.play().then(() => setIsPlaying(true));
+    else { audio.pause(); setIsPlaying(false); }
+  }, [current]);
+
+  const next = useCallback(() => {
+    if (index >= 0 && index < queue.length - 1) setIndex(index + 1);
+  }, [index, queue]);
+
+  const prev = useCallback(() => {
+    if (index > 0) setIndex(index - 1);
+  }, [index]);
+
+  const seek = useCallback((seconds) => {
+    audioRef.current.currentTime = seconds;
+  }, []);
+
+  return (
+    <MusicPlayerCtx.Provider value={{
+      current, isPlaying, progress, playAt, togglePlay, next, prev, seek,
+      hasNext: index < queue.length - 1, hasPrev: index > 0,
+      outputDevices, sinkId, sinkSupported, refreshOutputDevices, selectOutput,
+    }}>
+      {children}
+    </MusicPlayerCtx.Provider>
+  );
+};
+
+export const useMusicPlayer = () => useContext(MusicPlayerCtx);