Stemify iOS 1.1 and WebUI updates, repo restructure into desktop/ios/server/web

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

ios/Shared/MixIntents.swift

@@ -0,0 +1,68 @@
+import AppIntents
+
+/// What a widget or control button asks the player to do. [MixRemote] carries it out: the app's version drives
+/// the player, the widget extension's does nothing, since audio intents run in the app's process.
+enum MixAction: Sendable {
+    case cycle
+    case nudge(String, Int)
+    case mute(String)
+    case playPause
+}
+
+struct CycleMixIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Change Mix"
+    static let description = IntentDescription("Moves to the next stem mix, in the order set in the Stem Editor.")
+
+    init() {}
+
+    func perform() async throws -> some IntentResult {
+        await MixRemote.run(.cycle)
+        return .result()
+    }
+}
+
+struct NudgeStemIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Turn a Stem Up or Down"
+    static let isDiscoverable = false
+
+    @Parameter(title: "Stem") var stem: String
+    @Parameter(title: "Steps") var steps: Int
+
+    init() {}
+    init(stem: String, steps: Int) {
+        self.stem = stem
+        self.steps = steps
+    }
+
+    func perform() async throws -> some IntentResult {
+        await MixRemote.run(.nudge(stem, steps))
+        return .result()
+    }
+}
+
+struct MuteStemIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Mute or Unmute a Stem"
+    static let isDiscoverable = false
+
+    @Parameter(title: "Stem") var stem: String
+
+    init() {}
+    init(stem: String) { self.stem = stem }
+
+    func perform() async throws -> some IntentResult {
+        await MixRemote.run(.mute(stem))
+        return .result()
+    }
+}
+
+struct PlayPauseIntent: AudioPlaybackIntent {
+    static let title: LocalizedStringResource = "Play or Pause"
+    static let isDiscoverable = false
+
+    init() {}
+
+    func perform() async throws -> some IntentResult {
+        await MixRemote.run(.playPause)
+        return .result()
+    }
+}