Revert default protocol to SMB — UGreen NAS uses standard SMB

UGreen UGOS exposes personal folders as named SMB shares (e.g.
'personal_folder'). Third-party apps connect via SMB with the
UGOS username/password — no proprietary protocol involved.

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

Features/Connect/ConnectViewModel.swift

@@ -9,7 +9,7 @@ final class ConnectViewModel: ObservableObject {
     @Published var username = ""
     @Published var password = ""
     @Published var remotePath = "/"
-    @Published var selectedProtocol: NASProtocol = .sftp
+    @Published var selectedProtocol: NASProtocol = .smb
     @Published var isVerifying = false
     @Published var isConnected = false
     @Published var verifyError: String? = nil