Redesign ConnectView for UGreen NAS, default to SFTP

- Standalone IP field with hint labels below (matches UGreen connect pattern)
- Combined credentials card: username + hairline + password with show/hide eye
- Path field shows full absolute path (UGreen uses POSIX paths via SFTP)
- Default protocol changed from SMB → SFTP (UGreen absolute paths are SFTP-native)
- surfaceSunken background, protocol picker stays as secondary control
- Help button stub at bottom

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 = .smb
+    @Published var selectedProtocol: NASProtocol = .sftp
     @Published var isVerifying = false
     @Published var isConnected = false
     @Published var verifyError: String? = nil