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/UI/Components/AdaptiveDrawer.swift

@@ -0,0 +1,66 @@
+import SwiftUI
+
+/// Presents modal content in a native sheet. On phones it uses medium/large
+/// detents with a grabber; on wider layouts the sheet is form-sized. Content is
+/// wrapped in a `NavigationStack` so it gets a native title bar + Close button.
+struct AdaptiveDrawer<DrawerContent: View>: ViewModifier {
+	@Binding var isPresented: Bool
+	let windowClass: WindowClass
+	let onDismiss: () -> Void
+	@ViewBuilder let drawerContent: () -> DrawerContent
+
+	func body(content: Content) -> some View {
+		content.sheet(
+			isPresented: Binding(get: { isPresented }, set: { if !$0 { onDismiss() } })
+		) {
+			SheetChrome(onClose: onDismiss) { drawerContent() }
+				.modifier(PhoneDetents(enabled: windowClass == .phone))
+		}
+	}
+}
+
+private struct PhoneDetents: ViewModifier {
+	let enabled: Bool
+	func body(content: Content) -> some View {
+		if enabled {
+			content
+				.presentationDetents([.medium, .large])
+				.presentationDragIndicator(.visible)
+		} else {
+			content.frame(minWidth: 460, minHeight: 480)
+		}
+	}
+}
+
+private struct SheetChrome<Content: View>: View {
+	let onClose: () -> Void
+	@ViewBuilder let content: () -> Content
+
+	var body: some View {
+		NavigationStack {
+			ScrollView { content().padding(.top, 4) }
+				.toolbar {
+					ToolbarItem(placement: .cancellationAction) {
+						Button(String(localized: "button_close"), action: onClose)
+					}
+				}
+				#if os(iOS)
+				.navigationBarTitleDisplayMode(.inline)
+				#endif
+		}
+	}
+}
+
+extension View {
+	func adaptiveDrawer<DrawerContent: View>(
+		isPresented: Binding<Bool>,
+		windowClass: WindowClass,
+		onDismiss: @escaping () -> Void,
+		@ViewBuilder content: @escaping () -> DrawerContent
+	) -> some View {
+		modifier(AdaptiveDrawer(
+			isPresented: isPresented, windowClass: windowClass,
+			onDismiss: onDismiss, drawerContent: content
+		))
+	}
+}

apple/VniDrop/UI/Components/Buttons.swift

@@ -0,0 +1,50 @@
+import SwiftUI
+
+/// Native SwiftUI button styles. Purple accent comes from the app-wide `.tint`.
+
+/// Full-width filled button (`.borderedProminent`). Apply `.fixedSize()` at the
+/// call site to shrink it to its content.
+struct PrimaryButton: View {
+	let title: String
+	let action: () -> Void
+	var enabled: Bool = true
+
+	var body: some View {
+		Button(action: action) {
+			Text(title).frame(maxWidth: .infinity).frame(minHeight: 22)
+		}
+		.buttonStyle(.borderedProminent)
+		.controlSize(.large)
+		.disabled(!enabled)
+	}
+}
+
+/// Full-width bordered (secondary) button.
+struct SecondaryButton: View {
+	let title: String
+	let action: () -> Void
+	var enabled: Bool = true
+
+	var body: some View {
+		Button(action: action) {
+			Text(title).frame(maxWidth: .infinity).frame(minHeight: 22)
+		}
+		.buttonStyle(.bordered)
+		.controlSize(.large)
+		.disabled(!enabled)
+	}
+}
+
+/// Borderless tinted text button.
+struct QuietButton: View {
+	let title: String
+	let action: () -> Void
+	var enabled: Bool = true
+
+	var body: some View {
+		Button(title, action: action)
+			.buttonStyle(.borderless)
+			.disabled(!enabled)
+	}
+}
+

apple/VniDrop/UI/Components/Components.swift

@@ -0,0 +1,112 @@
+import SwiftUI
+
+// MARK: - StatusPill
+
+enum PillTone { case neutral, success, warning, destructive, brand }
+
+struct StatusPill: View {
+	let label: String
+	var tone: PillTone = .neutral
+
+	private var color: Color {
+		switch tone {
+		case .neutral: return .secondary
+		case .success, .brand: return VniDropColors.brandPurple
+		case .warning: return .orange
+		case .destructive: return .red
+		}
+	}
+
+	var body: some View {
+		HStack(spacing: 5) {
+			Circle().fill(color).frame(width: 6, height: 6)
+			Text(label).font(.caption).fontWeight(.medium).foregroundStyle(color).lineLimit(1)
+		}
+		.padding(.horizontal, 9).padding(.vertical, 4)
+		.background(color.opacity(0.14), in: Capsule())
+	}
+}
+
+// MARK: - ProgressRow
+
+struct ProgressRow: View {
+	let labelKey: String
+	let progress: Double?
+	var detail: String? = nil
+
+	var body: some View {
+		VStack(alignment: .leading, spacing: 4) {
+			HStack {
+				Text(LocalizedStringKey(labelKey)).font(.subheadline).lineLimit(1)
+				Spacer()
+				if let progress {
+					Text("\(Int(progress * 100))%").font(.caption).foregroundStyle(.secondary)
+				}
+			}
+			if let detail {
+				Text(detail).font(.caption).foregroundStyle(.secondary).lineLimit(1)
+			}
+			if let progress {
+				ProgressView(value: progress)
+			} else {
+				ProgressView().progressViewStyle(.linear)
+			}
+		}
+		.frame(maxWidth: .infinity)
+	}
+}
+
+// MARK: - Field
+
+/// Labeled text field using native styling. Renders cleanly both inside a `Form`
+/// row and standalone (e.g. inside a sheet).
+struct Field: View {
+	let label: String
+	@Binding var value: String
+	var minLines: Int = 1
+	var enabled: Bool = true
+
+	var body: some View {
+		VStack(alignment: .leading, spacing: 6) {
+			Text(label).font(.subheadline).foregroundStyle(.secondary)
+			Group {
+				if minLines > 1 {
+					TextField(label, text: $value, axis: .vertical)
+						.lineLimit(minLines, reservesSpace: true)
+				} else {
+					TextField(label, text: $value)
+				}
+			}
+			.textFieldStyle(.roundedBorder)
+			.disabled(!enabled)
+		}
+	}
+}
+
+// MARK: - EmptyStateView
+
+/// Native-styled empty state (iOS 16 compatible; avoids iOS 17
+/// `ContentUnavailableView`).
+struct EmptyStateView<Actions: View>: View {
+	let systemImage: String
+	let title: String
+	let message: String
+	@ViewBuilder var actions: () -> Actions
+
+	var body: some View {
+		VStack(spacing: 12) {
+			Image(systemName: systemImage)
+				.font(.system(size: 52))
+				.foregroundStyle(.secondary)
+			Text(title).font(.title2).fontWeight(.semibold).multilineTextAlignment(.center)
+			Text(message)
+				.font(.body).foregroundStyle(.secondary)
+				.multilineTextAlignment(.center)
+				.frame(maxWidth: 420)
+			actions().padding(.top, 4)
+		}
+		.frame(maxWidth: .infinity)
+		.padding(.horizontal, 24)
+		.padding(.vertical, 48)
+	}
+}

apple/VniDrop/UI/Components/PlatformImage.swift

@@ -0,0 +1,20 @@
+import SwiftUI
+
+/// Cross-platform decoding of raw image bytes into a SwiftUI `Image`.
+enum PlatformImage {
+	static func from(data: Data) -> Image? {
+		#if os(iOS)
+		guard let ui = UIImage(data: data) else { return nil }
+		return Image(uiImage: ui)
+		#else
+		guard let ns = NSImage(data: data) else { return nil }
+		return Image(nsImage: ns)
+		#endif
+	}
+}
+
+#if os(iOS)
+import UIKit
+#else
+import AppKit
+#endif