Initial scaffold — NASBackup iOS app

Full project scaffold: XcodeGen project.yml, Core models/protocols/errors,
SMBService (kishikawakatsumi/SMBClient), SFTPService (Citadel 0.9.2),
PhotoLibraryService, LANMonitor, BackupEngine, BackgroundTaskManager,
all feature UIs (Login, Connect, Browse, Backup, History, Settings),
Shared components and theme. Builds clean with zero errors.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Features/Connect/ConnectViewModel.swift

@@ -0,0 +1,53 @@
+import Foundation
+
+enum ConnectField { case host, username, password, folder }
+enum FieldState { case idle, valid, invalid }
+
+@MainActor
+final class ConnectViewModel: ObservableObject {
+    @Published var host = ""
+    @Published var username = ""
+    @Published var password = ""
+    @Published var remotePath = "/"
+    @Published var selectedProtocol: NASProtocol = .smb
+    @Published var isVerifying = false
+    @Published var isConnected = false
+    @Published var verifyError: String? = nil
+    @Published var showFolderBrowser = false
+
+    var fieldState: FieldState {
+        isConnected ? .valid : (verifyError != nil ? .invalid : .idle)
+    }
+
+    var canConnect: Bool {
+        !host.isEmpty && !username.isEmpty && !password.isEmpty && !isVerifying
+    }
+
+    func verify() async {
+        isVerifying = true
+        isConnected = false
+        verifyError = nil
+
+        let connection = NASConnection(
+            host: host,
+            nasProtocol: selectedProtocol,
+            username: username,
+            password: password,
+            remotePath: remotePath
+        )
+
+        let service: any NASTransferProtocol = selectedProtocol == .smb ? SMBService() : SFTPService()
+        do {
+            try await service.connect(to: connection.host, port: connection.port,
+                                      username: connection.username, password: connection.password)
+            service.disconnect()
+            isConnected = true
+            ConnectionStore.shared.savedConnection = connection
+        } catch let e as BackupError {
+            verifyError = e.errorDescription
+        } catch {
+            verifyError = error.localizedDescription
+        }
+        isVerifying = false
+    }
+}