Add local Live Activity and Dynamic Island track display

Shared/MusicActivityAttributes.swift

@@ -0,0 +1,26 @@
+import ActivityKit
+import Foundation
+
+struct MusicActivityAttributes: ActivityAttributes {
+    struct ContentState: Codable, Hashable {
+        var title: String
+        var artist: String
+        var playing: Bool
+        var position: Double
+        var duration: Double
+        var updatedAt: Date
+        var connected: Bool
+
+        // Bound UTF-8, including pathological combining characters, below ActivityKit's 4 KB limit.
+        static func bounded(_ text: String) -> String {
+            var result = ""
+            for scalar in text.unicodeScalars {
+                guard result.utf8.count + scalar.utf8.count <= 256 else { break }
+                result.unicodeScalars.append(scalar)
+            }
+            return result
+        }
+
+        var progress: Double { duration > 0 ? min(1, max(0, position / duration)) : 0 }
+    }
+}

Shared/MusicActivityViews.swift

@@ -0,0 +1,46 @@
+import SwiftUI
+
+struct MusicActivityCard: View {
+    let state: MusicActivityAttributes.ContentState
+    let stale: Bool
+    var body: some View {
+        VStack(alignment: .leading, spacing: 10) {
+            HStack(spacing: 12) {
+                Image(systemName: "waveform").font(.title).foregroundStyle(.indigo)
+                TrackLabels(state: state)
+                Spacer(minLength: 0)
+                Image(systemName: state.playing ? "play.fill" : "pause.fill")
+                    .accessibilityLabel("Последнее состояние: " + (state.playing ? "воспроизведение" : "пауза"))
+            }
+            ProgressView(value: state.progress).tint(.indigo)
+            ActivityStatus(state: state, stale: stale)
+            Label("Открыть плеер", systemImage: "arrow.up.forward.app").font(.caption.weight(.semibold))
+        }.padding(16)
+    }
+}
+
+struct TrackLabels: View {
+    let state: MusicActivityAttributes.ContentState
+    var body: some View {
+        VStack(alignment: .leading, spacing: 3) {
+            Text(state.title).font(.headline).lineLimit(1)
+            Text(state.artist.isEmpty ? "MusicBridge · музыка на ПК" : state.artist)
+                .font(.caption).foregroundStyle(.secondary).lineLimit(1)
+        }
+    }
+}
+
+struct ActivityStatus: View {
+    let state: MusicActivityAttributes.ContentState
+    let stale: Bool
+    var body: some View {
+        if stale || !state.connected {
+            Text("Данные устарели · откройте плеер").font(.caption).foregroundStyle(.secondary)
+        } else {
+            HStack(spacing: 4) {
+                Text("Снимок с ПК в")
+                Text(state.updatedAt, style: .time)
+            }.font(.caption).foregroundStyle(.secondary)
+        }
+    }
+}