feat(remote): wire HostServer and RemoteClient into MusicApp with menu items and DB swap

Music/ContentView.swift

@@ -9,6 +9,7 @@ struct ContentView: View {
     var shazam: ShazamService
     var db: DatabaseService
     @Binding var showNewPlaylistAlert: Bool
+    var networkStatus: NetworkStatus?
     @State private var showRenameAlert = false
     @State private var showEditQueryAlert = false
     @State private var playlistNameInput = ""

Music/MusicApp.swift

@@ -11,6 +11,9 @@ struct MusicApp: App {
     @State private var playlistVM: PlaylistViewModel?
     @State private var showNewPlaylistAlert = false
     @State private var initError: String?
+    @State private var hostServer: HostServer?
+    @State private var remoteClient = RemoteClient()
+    @State private var showConnectionSheet = false
 
     var body: some Scene {
         WindowGroup {
@@ -27,7 +30,8 @@ struct MusicApp: App {
                         playlist: playlist,
                         shazam: shazamService,
                         db: db,
-                        showNewPlaylistAlert: $showNewPlaylistAlert
+                        showNewPlaylistAlert: $showNewPlaylistAlert,
+                        networkStatus: computeNetworkStatus()
                     )
                 } else if let error = initError {
                     Text("Failed to initialize database: \(error)")
@@ -38,6 +42,16 @@ struct MusicApp: App {
                 }
             }
             .frame(minWidth: 800, minHeight: 500)
+            .onChange(of: remoteClient.connectionState) { _, newState in
+                if case .connected = newState {
+                    enterRemoteMode()
+                } else if newState == .disconnected {
+                    exitRemoteMode()
+                }
+            }
+            .sheet(isPresented: $showConnectionSheet) {
+                ConnectionSheet(remoteClient: remoteClient, isPresented: $showConnectionSheet)
+            }
         }
         .commands {
             CommandGroup(after: .newItem) {
@@ -45,11 +59,27 @@ struct MusicApp: App {
                     pickFolder()
                 }
                 .keyboardShortcut("o")
+                .disabled(remoteClient.connectionState.isConnected)
 
                 Button("New Playlist...") {
                     showNewPlaylistAlert = true
                 }
                 .keyboardShortcut("n")
+                .disabled(remoteClient.connectionState.isConnected)
+
+                Divider()
+
+                Toggle("Enable Host Mode", isOn: Binding(
+                    get: { hostServer?.isHosting ?? false },
+                    set: { $0 ? startHosting() : hostServer?.stop() }
+                ))
+                .disabled(remoteClient.connectionState.isConnected)
+
+                Button("Connect to Remote...") {
+                    showConnectionSheet = true
+                    remoteClient.startDiscovery()
+                }
+                .disabled(hostServer?.isHosting ?? false)
             }
         }
     }
@@ -144,4 +174,69 @@ struct MusicApp: App {
             return nil
         }
     }
+
+    // MARK: - Remote / Host
+
+    private func startHosting() {
+        guard let db = dbService, let player = playerVM else { return }
+        let appSupport = FileManager.default.urls(
+            for: .applicationSupportDirectory, in: .userDomainMask
+        ).first!.appendingPathComponent("Music", isDirectory: true)
+        let dbPath = appSupport.appendingPathComponent("db.sqlite").path
+
+        let server = HostServer(dbPath: dbPath)
+        server.configure(player: player, db: db)
+        do {
+            try server.start()
+            hostServer = server
+        } catch {
+            print("Failed to start host: \(error)")
+        }
+    }
+
+    private func enterRemoteMode() {
+        guard let player = playerVM else { return }
+        do {
+            let remoteDb = try DatabaseService(path: RemoteClient.remoteDBPath)
+            self.libraryVM = LibraryViewModel(db: remoteDb)
+            self.playlistVM = PlaylistViewModel(db: remoteDb)
+
+            player.enterRemoteMode(client: remoteClient)
+            player.trackResolver = { trackId in
+                self.libraryVM?.tracks.first(where: { $0.id == trackId })
+            }
+
+            remoteClient.onPlaybackState = { [weak player] state in
+                player?.applyRemoteState(state)
+            }
+        } catch {
+            print("Failed to load remote DB: \(error)")
+            remoteClient.disconnect()
+        }
+    }
+
+    private func exitRemoteMode() {
+        playerVM?.exitRemoteMode()
+        remoteClient.onPlaybackState = nil
+        guard let db = dbService else { return }
+        self.libraryVM = LibraryViewModel(db: db)
+        self.playlistVM = PlaylistViewModel(db: db)
+        try? FileManager.default.removeItem(atPath: RemoteClient.remoteDBPath)
+    }
+
+    private func computeNetworkStatus() -> NetworkStatus? {
+        if remoteClient.connectionState.isConnected {
+            let hostName: String
+            if case .connected(let name) = remoteClient.connectionState { hostName = name } else { hostName = "Unknown" }
+            return NetworkStatus(
+                mode: .remote(hostName: hostName),
+                onDisconnect: { [remoteClient] in remoteClient.disconnect() },
+                onRefreshLibrary: { [remoteClient] in remoteClient.sendCommand(.refreshDB) }
+            )
+        }
+        if let server = hostServer, server.isHosting {
+            return NetworkStatus(mode: .hosting(connectedRemote: server.connectedRemoteName))
+        }
+        return nil
+    }
 }