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/App/AppGraph.swift

@@ -0,0 +1,43 @@
+import Foundation
+import Combine
+
+/// Object graph wiring the repositories and coordinators together, ported from
+/// `AppGraph.kt`. Owned by the app root for the process lifetime.
+@MainActor
+final class AppGraph: ObservableObject {
+	let dependencies: AppDependencies
+	let coreRepository: CoreRepository
+	let visibility = AppVisibility()
+	let messages = UiMessageController()
+	let preferencesRepository: AppPreferencesRepository
+	let filePreviewRepository: FilePreviewRepository
+	let approvalCoordinator: ApprovalCoordinator
+
+	init(dependencies: AppDependencies, coreRepository: CoreRepository? = nil) {
+		self.dependencies = dependencies
+		let coreRepository = coreRepository ?? CoreRepository()
+		self.coreRepository = coreRepository
+		self.filePreviewRepository = FilePreviewRepository(appDataDir: dependencies.environment.defaultCoreDataDir)
+		self.preferencesRepository = AppPreferencesRepository(
+			fallback: AppPreferencesDefaults(
+				username: dependencies.environment.defaultUsername,
+				receiveFolder: dependencies.fileSystemService.defaultReceiveFolder(),
+				themeMode: .system,
+				notificationsEnabled: false,
+				diagnosticsEnabled: false
+			)
+		)
+		self.approvalCoordinator = ApprovalCoordinator(
+			repository: coreRepository,
+			preferences: preferencesRepository,
+			notifications: dependencies.notificationService,
+			visibility: visibility,
+			messages: messages
+		)
+		AppLogger.info("lifecycle", "graph created", ["platform": dependencies.environment.name])
+	}
+
+	func close() {
+		coreRepository.shutdown()
+	}
+}