feat(apple): native SwiftUI app for iOS and macOS

Add a native SwiftUI VniDrop app (Send/Receive/Settings) talking to the
Rust core via generated UniFFI Swift bindings, plus the uniffi-bindgen
helper crate. iOS uses a TabView, macOS a NavigationSplitView sidebar.

apple/VniDrop/Core/LocalNotificationService.swift

@@ -0,0 +1,103 @@
+import Foundation
+import Combine
+import UserNotifications
+
+/// Notification permission state, ported from `NotificationPermission`.
+enum NotificationPermission {
+	case notDetermined
+	case granted
+	case denied
+	case unsupported
+}
+
+struct LocalNotification {
+	let id: String
+	let title: String
+	let body: String
+}
+
+/// Local notification service, ported from `LocalNotificationService.kt` /
+/// `.ios.kt`, backed by `UNUserNotificationCenter`.
+@MainActor
+final class LocalNotificationService: ObservableObject {
+	@Published private(set) var permission: NotificationPermission = .notDetermined
+
+	private let center = UNUserNotificationCenter.current()
+
+	func refreshPermission() async -> NotificationPermission {
+		let settings = await center.notificationSettings()
+		let mapped = Self.map(settings.authorizationStatus)
+		permission = mapped
+		return mapped
+	}
+
+	func requestPermission() async -> NotificationPermission {
+		do {
+			_ = try await center.requestAuthorization(options: [.alert, .sound, .badge])
+		} catch {
+			AppLogger.error("notifications", "authorization request failed", error)
+		}
+		return await refreshPermission()
+	}
+
+	func openSettings() async -> Result<Void, Error> {
+		#if os(iOS)
+		guard let url = URL(string: UIApplication.openSettingsURLString) else {
+			return .failure(NotificationError.settingsUnavailable)
+		}
+		let opened = await UIApplication.shared.open(url)
+		return opened ? .success(()) : .failure(NotificationError.settingsUnavailable)
+		#else
+		guard let url = URL(string: "x-apple.systempreferences:com.apple.preference.notifications") else {
+			return .failure(NotificationError.settingsUnavailable)
+		}
+		NSWorkspace.shared.open(url)
+		return .success(())
+		#endif
+	}
+
+	@discardableResult
+	func publish(_ notification: LocalNotification) async -> Result<Void, Error> {
+		let content = UNMutableNotificationContent()
+		content.title = notification.title
+		content.body = notification.body
+		content.sound = .default
+		let request = UNNotificationRequest(identifier: notification.id, content: content, trigger: nil)
+		do {
+			try await center.add(request)
+			return .success(())
+		} catch {
+			return .failure(error)
+		}
+	}
+
+	func cancel(id: String) {
+		center.removePendingNotificationRequests(withIdentifiers: [id])
+		center.removeDeliveredNotifications(withIdentifiers: [id])
+	}
+
+	func cancelAll() {
+		center.removeAllPendingNotificationRequests()
+		center.removeAllDeliveredNotifications()
+	}
+
+	private static func map(_ status: UNAuthorizationStatus) -> NotificationPermission {
+		switch status {
+		case .authorized, .provisional, .ephemeral: return .granted
+		case .denied: return .denied
+		case .notDetermined: return .notDetermined
+		@unknown default: return .notDetermined
+		}
+	}
+}
+
+private enum NotificationError: LocalizedError {
+	case settingsUnavailable
+	var errorDescription: String? { "Could not open notification settings" }
+}
+
+#if os(iOS)
+import UIKit
+#else
+import AppKit
+#endif