Polish AddSourceView layout on tvOS

Add a TVSourceRowLabelStyle for consistent icon/text spacing, switch
the Scan Network button to TVFormRowButtonStyle so it matches the
NavigationLink rows, and drop the duplicate navigationTitle in
AddWebDAV/AddSMB views since the title is already shown in the
TVSidebarDetailContainer sidebar.

Yattee/Views/Settings/AddSource/AddSMBView.swift

@@ -54,10 +54,12 @@ struct AddSMBView: View {
         #if os(iOS)
         .scrollDismissesKeyboard(.interactively)
         #endif
+        #if !os(tvOS)
         .navigationTitle(String(localized: "sources.addSMB"))
         #if os(iOS)
         .navigationBarTitleDisplayMode(.inline)
         #endif
+        #endif
         .onAppear {
             if let prefillServer {
                 server = prefillServer