Web player overhaul; iOS random sort, stems-only filter, pooled libraries

Web: live Stem Now status that tracks every queued song (albums too),
right-click menus with Stem Now, Songs and Genres pages, a Stems Only
filter in place of the sidebar section, Random sort, several pooled
Plex servers and libraries, themes plus custom CSS, a reorganised
settings page that loads without a refresh, saved mixes, karaoke and
synced lyrics, stem playlists and offline downloads.

iOS: Random in every sort menu, a Stems Only toggle (sort menu and
Settings), and several music libraries pooled from the signed-in server.
Settings now persists karaoke and speed across launches.

stemd writes a status file that stemserve serves at /api/queue.

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

ios/Stemify/Core/Settings.swift

@@ -103,6 +103,7 @@ final class Settings: @unchecked Sendable {
         "plexUrl", "plexToken", "plexUser", "plexMachineId", "musicSection", "musicSectionTitle",
         "stemUrl", "stemToken", "stemRoots", "theme", "accent", "albumColorNowPlaying", "highRefreshRate",
         "stemQuality", "cacheLimitGb", "downloadsWifiOnly", "downloadSort", "keepStemMix", "masterVolume", "tabLayout",
+        "karaokeVocals", "karaokeSoftDb", "playbackSpeed", "stemsOnly",
     ]
 
     private func read<T>(_ kp: KeyPath<Settings, T>, _ key: String, _ def: T) -> T {
@@ -189,6 +190,8 @@ final class Settings: @unchecked Sendable {
     var karaokeVocals: Int { get { read(\.karaokeVocals, "karaokeVocals", KaraokeVocals.Off.rawValue) } set { write(\.karaokeVocals, "karaokeVocals", newValue, KaraokeVocals.Off.rawValue) } }
     /// How far down Soft karaoke puts the vocals, in dB.
     var karaokeSoftDb: Int { get { read(\.karaokeSoftDb, "karaokeSoftDb", -12) } set { write(\.karaokeSoftDb, "karaokeSoftDb", newValue, -12) } }
+    /// Library lists show only what has stems.
+    var stemsOnly: Bool { get { read(\.stemsOnly, "stemsOnly", false) } set { write(\.stemsOnly, "stemsOnly", newValue, false) } }
     var keepStemMix: Bool { get { read(\.keepStemMix, "keepStemMix", true) } set { write(\.keepStemMix, "keepStemMix", newValue, true) } }
     var playbackSpeed: Double {
         get { access(keyPath: \.playbackSpeed); lock.lock(); defer { lock.unlock() }; return (store["playbackSpeed"] as? NSNumber)?.doubleValue ?? 1 }