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/CoreModels.swift

@@ -0,0 +1,141 @@
+import Foundation
+
+/// App-facing domain models, ported from `core/CoreModels.kt`. The repository maps
+/// the generated UniFFI records/enums into these so the UI never depends on the
+/// binding surface directly.
+
+struct CoreStatus: Equatable {
+	let endpointId: String
+	let activeTransfers: UInt64
+	let activeShares: UInt64
+}
+
+struct CoreEventModel: Equatable, Identifiable {
+	let id: String
+	let timestamp: Int64
+	let scope: String
+	let transferId: UInt64?
+	let direction: String?
+	let phase: String
+	let kind: String
+	let dataJson: String
+}
+
+enum ShareAccessPolicy: Equatable {
+	case requireApproval
+	case anyoneWithTransfer
+}
+
+enum TransferDirection: Equatable {
+	case send
+	case receive
+}
+
+enum TransferStatus: Equatable {
+	case importing
+	case sharing
+	case receiving
+	case done
+	case failed
+	case cancelled
+	case stopped
+}
+
+struct Transfer: Equatable, Identifiable {
+	let localId: String
+	let transferId: UInt64
+	let direction: TransferDirection
+	let status: TransferStatus
+	let peerId: String?
+	let transferName: String?
+	let contentHash: String?
+	let fileCount: UInt64
+	let totalSize: UInt64
+	let ticket: String?
+	let accessPolicy: ShareAccessPolicy
+	let createdAt: Int64
+	let updatedAt: Int64
+
+	var id: String { localId }
+}
+
+struct Share: Equatable {
+	let transferId: UInt64
+	let ticket: String
+	let transferName: String
+	let contentHash: String
+	let fileCount: UInt64
+	let totalSize: UInt64
+}
+
+struct TransferMetadataModel: Equatable {
+	let transferId: UInt64
+	let transferName: String
+	let senderName: String?
+	let contentHash: String
+	let fileCount: UInt64
+	let totalSize: UInt64
+}
+
+struct TicketInspectionModel: Equatable {
+	let kind: String
+	let metadata: TransferMetadataModel
+}
+
+enum ReceiverDeliveryStatus: Equatable {
+	case requested
+	case accepted
+	case refused
+	case expired
+	case completed
+	case unknown
+}
+
+struct ReceiverRequestModel: Equatable, Identifiable {
+	let id: String
+	let transferId: UInt64
+	let remoteEndpointId: String
+	let transferName: String
+	let receiverName: String?
+	let receiverDeviceName: String?
+	let appVersion: String
+	let status: ReceiverDeliveryStatus
+	let reason: String?
+	let requestedAt: Int64
+	let respondedAt: Int64?
+	let completedAt: Int64?
+}
+
+struct CoreState: Equatable {
+	var isInitialized: Bool = false
+	var status: CoreStatus?
+	var events: [CoreEventModel] = []
+	var transfers: [Transfer] = []
+	var lastShare: Share?
+	var lastInspection: TicketInspectionModel?
+}
+
+/// Coalesced change hints emitted from the event sink, ported from `CoreSignal`.
+enum CoreSignal: Equatable {
+	case approvalChanged(transferId: UInt64)
+	case receiverHistoryChanged(transferId: UInt64)
+	/// Transfer status/history changed enough to re-read the durable snapshot.
+	case transfersChanged(transferId: UInt64)
+}
+
+// MARK: - Transfer helpers (ported from AppUiModels.kt)
+
+extension TransferStatus {
+	var isActiveTransfer: Bool {
+		self == .importing || self == .sharing || self == .receiving
+	}
+
+	var canCancelTransfer: Bool {
+		self == .importing || self == .sharing || self == .receiving
+	}
+
+	/// Terminal receive-history states eligible for deletion.
+	var isTerminalReceiveHistory: Bool {
+		self == .done || self == .failed || self == .cancelled
+	}
+}