chore: scaffold Voice iOS app (Phase 0)

XcodeGen project, SwiftUI iOS 17 target dev.shane.voice, SPM
livekit-client-swift 2.16.0, mic usage + ATS LAN exception in
Info.plist, placeholder conversation screen and Settings with
server URL field.

Sources/App/SettingsStore.swift

@@ -0,0 +1,41 @@
+import Foundation
+import Combine
+
+final class SettingsStore: ObservableObject {
+    @Published var serverURL: String {
+        didSet { UserDefaults.standard.set(serverURL, forKey: Keys.serverURL) }
+    }
+    @Published var voiceID: String {
+        didSet { UserDefaults.standard.set(voiceID, forKey: Keys.voiceID) }
+    }
+    @Published var modelID: String? {
+        didSet { UserDefaults.standard.set(modelID, forKey: Keys.modelID) }
+    }
+    @Published var textMode: Bool {
+        didSet { UserDefaults.standard.set(textMode, forKey: Keys.textMode) }
+    }
+    @Published var volume: Double {
+        didSet { UserDefaults.standard.set(volume, forKey: Keys.volume) }
+    }
+
+    private enum Keys {
+        static let serverURL = "serverURL"
+        static let voiceID = "voiceID"
+        static let modelID = "modelID"
+        static let textMode = "textMode"
+        static let volume = "volume"
+    }
+
+    init() {
+        let d = UserDefaults.standard
+        serverURL = d.string(forKey: Keys.serverURL) ?? "https://192.168.86.2:9178"
+        voiceID = d.string(forKey: Keys.voiceID) ?? ""
+        modelID = d.string(forKey: Keys.modelID)
+        textMode = d.bool(forKey: Keys.textMode)
+        volume = d.object(forKey: Keys.volume) as? Double ?? 0.8
+    }
+
+    var trimmedServerURL: String {
+        serverURL.trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+}

Sources/App/VoiceApp.swift

@@ -0,0 +1,13 @@
+import SwiftUI
+
+@main
+struct VoiceApp: App {
+    @StateObject private var settings = SettingsStore()
+
+    var body: some Scene {
+        WindowGroup {
+            ConversationView(settings: settings)
+                .preferredColorScheme(.dark)
+        }
+    }
+}